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Education / Training The power band of a precharged airgun

The power band of a precharged airgun

by Tom Gaylord
Writing as B.B. Pelletier

This report covers:

  • Difference between a precharged airgun and a multi-pump
  • Balanced valve
  • Benjamin 700
  • Benjamin 710
  • Benjamin 600 Automatic
  • How a PCP valve works
  • Run out of barrel
  • Power band = 1000 psi?
  • The power curve
  • Why don’t they…?
  • What should you do?
  • Last tip — worth the price

The topic for today’s report comes from reader GunFun 1, who asked me to discuss the useful power band of a precharged pneumatic (PCP). Some of you are thinking about getting into PCPs and you wonder how they work. Today’s report should clarify some of that for you.

Difference between a precharged airgun and a multi-pump

I’ll start with the main difference between a multi-pump and a PCP. A multi-pump like the Benjamin 392 that many of you are familiar with, fills with air that you pump in manually. It all gets exhausted with the one shot, or at least it is supposed to. Fill with many pumps and then exhaust all at once — that’s something many airgunners know.

Sometimes the valve in a multi-pump can’t exhaust all the air. The striker spring weakened over time. When that happens, a second shot can be fired without pumping the gun. That shot is usually very weak, although as the spring degrades, it can become more and more powerful, until it has some real power of its own! What is happening is the valve is not exhausting all the air on the first shot and some of it remains in the gun for a second shot. This is what happens with a precharged gun, only it is planned and the second shot is very close in power to the first. And so is shot number three and so on.

Balanced valve

It would be possible to create a multi-pump that fires a second shot powerfully. All that’s needed is a striker spring that’s weak enough, a valve return spring with the correct tension and a valve orifice and valve seat shape that exhausts air in smaller amounts. We already know that it happens to multi-pumps though wear, but it can also be planned and designed into the airgun.

Benjamin 700

The Benjamin 700 from 1937 was a 25-shot BB gun that was pumped 12 times, then got about four powerful shots before needing to be topped off with a few more pump strokes. It was advertised that way, so Benjamin meant for it to be used that way. They were apparently fascinated with the performance, and continued to advance the design in the model 710.

Benjamin 710

The Benjamin 710 of 1939 is another 25-shot BB gun, only this one gets pumped up to 20 times and gets 6 to 8 powerful shots on one fill. This one they advertised could maintain full power with one or two pumps after each shot. This was the last model of the 700-series that got multiple shots from a single fill of air. The model 720 was also a 25-shot BB gun, but it had to be pumped after every shot.

Benjamin 600 Automatic

This BB gun is a semiautomatic that keeps firing as fast as the trigger is pulled. Fill it with as much air as you can pump. It’s a front-pumper, so it won’t be that many strokes. Benjamin’s instructions say to fill it as much as you can, which they say depends on what you weigh. From this you should get 10-12 shots before refilling.

I could continue, but you get the idea. That fact is Benjamin made several pneumatics that got many shots per fill. All you have to do to make a gun like this into a PCP is take away the onboard hand pump and fill the gun from a separate source.

How a PCP valve works

The information above illustrates how a powerplant and its firing valve can be set up to release just a portion of the air stored in the reservoir, keeping the rest for follow-on shots. All it takes is some thought to enlarge the reservoir to get even more shots per fill and to adjust the valve to use that compressed air as sparingly as possible. But something else creeps into the equation at this point.

With the Benjamin multi-pumps described above, each successive shot was less powerful until all the air was exhausted. But PCPs don’t work that way. A PCP will continue to shoot all its shots within a reasonably tight velocity spread, even though the air pressure inside the reservoir is constantly dropping. They can do that because when the valve releases air, it stays behind the pellet and holds the valve open for a brief time. If the barrel is long enough, the pellet stays inside for some time and allows the air pressure behind it to continue to build because the valve has not yet closed.

If the valve did close, then each shot would be a little slower than the last. But because the air valve remains open just a little longer each time, more air leaves the reservoir. Yes it is pressurized a little less each time, but there is more of it because the valve remains open just a little longer and that balances things out. As a result, the pellet gets a longer push from lower pressure air, which keeps the pellet velocity more or less the same.

Run out of barrel

At some point, though, the pellet has to leave the muzzle and the push has to stop. When that happens, the pellet velocity starts dropping with every successive shot and we say the gun is off the power curve.

Power band = 1000 psi?
GunFun 1 mentioned that he has noticed that many PCPs seem to have their power band — the pressure at which all the shots seem to go out at about the same velocity — in a range of pressures that’s about 1,000 psi, high to low. But he then said that his Talon SS is only filled to 2700 psi and runs out of steam at 2000 psi, which is only 700 psi. The lesson here is that 1000 psi is not a magic number, any more than a fill pressure of 3000 psi is magic. And please note that the Talon SS has a 12-inch barrel, although I don’t know if GunFun1 has replaced his barrel or not. I’m just saying that a shorter barrel will have a narrower power band.

When I worked at AirForce Airguns I used to take angry calls from customers wanting to know why their AirForce Condor could only be filled to 2650 psi, when it “should” have filled to 3000 psi. They tried putting in more air, but their gun just shot slower when they did. They were still getting the top velocity the gun could give (1,250 f.p.s. with .22 caliber Crosman Premiers) and they were getting it over 20 shots, which is all a Condor will do at top velocity, but they wondered why they were being “cheated” by having their gun stop 350 psi below the place where it “should” stop.

The power curve

These shooters did not understand how precharged airguns work. You don’t use an arbitrary fill pressure to determine the gun’s power. You use a chronograph. You fill the gun until any higher pressure results in slower shots. That pressure is the maximum fill pressure — regardless of what number that turns out to be. Then you shoot the gun until the velocity starts dropping off rapidly. Fill it again and note the pressure at which the tank begins to accept air. That is your lower pressure limit.

The band of pressure between the highest fill pressure and the lowest pressure at which the shots are still stable is called the power curve. Don’t try to make that curve conform to certain numbers. Just find out where it is and live with it. The high number is your maximum fill pressure and the low number is the point where your gun needs to be filled.

As it turns out, many times the power curve for a particular airgun will be about 1,000 psi., but it doesn’t have to be. It is whatever it is, and you find that out with a chronograph. Typically PCPs with shorter barrels will have narrower power bands, as will the more powerful guns. A lower-powered PCP and one with a longer barrel will have a larger band of pressure. But, until you use a chronograph to find out, you’ll never know for sure.

Why don’t they…?

And this is where the armchair engineers pipe in with all their suggestions for building better airguns. If only the engineers that designed PCPs would make them with broader power bands so we would get more shots from a fill. That’s so obvious that they wonder why no one has thought of it before.

Well, relax, because “they” have thought of it. In fact, “they” are constantly working with things like air transfer port diameters and length, striker weights and strokes and valve return spring strengths and striker de-bounce devices and so on. “They” have even resorted to electronically operated valves that are computer controlled. “They” have given us the very best “they” can, thus far, and “they” will continue to work on improving things in the future. But until then, power bands will probably not exceed 1,000 psi and many times they will be narrower.

What should you do?

Now that you know this, what should you do about it? Glad you asked. I’m assuming you want to apply it to a precharged airgun. First, get a chronograph. You don’t need a chronograph to enjoy a precharged airgun, but you will never know exactly where the power band is without one.

Use the published fill pressure as a starting point — a guideline. I have seen plenty precharged airguns without a regulator whose maximum fill pressures were not what was published or even what was engraved on the side of the gun. If it says 3000 psi, expect something between 2800 and 3100 psi. That’s why you test every airgun.

I have found that the lower the fill pressure the closer the number usually comes to the actual maximum. I have owned two different Daystates that filled to 2600 psi, and they both tested to within 100 psi of that. A hand-built gun like a USFT is probably tested by the builder before you get it. If a gun like that is off, it will be because your gauge doesn’t agree with the maker’s.

The point is, you only discover the power band of a PCP by testing for it. The test is simple if you have a chronograph. Without it, you are just guessing.

Last tip — worth the price

My last tip today. What if you don’t have a chronograph and can’t afford one? Is there any way to know what your power band is? Yes, there is.

You may not know the velocity the gun is delivering, but you can discover where the power band is by shooting a large group of shots at a target long distance away. First, fill to where you think the maximum is. Then start shooting at a target a long way off — at least 40 yards. If the pellets walk up in the beginning, the gun was over-pressurized. If they group together and then start to drop, the gun was on the power band until the pellets started to drop. That’s when it came off the power band. I actually did this with my first Career 707 rifle.

Just remember, you don’t need a lot of extra equipment to enjoy an airgun. But if you want to understand the technical parameters, some equipment is vital.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

121 thoughts on “The power band of a precharged airgun”

  1. Hi BB.

    I’m going to start you off with a Why don’t they question or something similar.

    My question is what happened that Benjamin decided building multi-shot pump-ups was a bad idea?

    And, if it is reasonably within the parameters of engineering know-how, why don’t “they” create another, better one? There must be reasons, but I don’t know what they are. I’d like to have one but maybe there isn’t enough demand? Or, are there other reasons?

  2. BB
    First thanks for writing today’s report. Alot alot of good info here today.

    And my Talon SS has a 12″ .22 caliber barrel. And I have to bring something else up.

    You mentioned how the pellet stays in the barrel in a sense it helps regulate the air used I believe anyway. I was going to mention this when the idea came up about today’s report. But I wanted to wait till today.

    Well I found that a heavier pellet shot from a pcp with even a shorter barrel will give a narrower powerband. Or could we call it more efficient use of the air. In other words I tend to get more usable shots per fill with a heavier pellet when shot from a pcp gun.

    And that brings me to your shooting advise at the end of the report today. That is a excellent way to determine what a pcp guns powerband is. By shooting and watching what the pellet impact is like throughout the fill pressure range. A good example of that being a good way to determine a guns usable shots is a Co2 gun.

    The Crosman 1077 on a 12 gram Co2 cartridge is a excellent way to learn how the powerband works by shooting results. Remember your 12 gram Co2 has no pressure gauge to let you know what’s left in the cartridge or where its start pressure is. So how do you know when the guns getting its most efficient shots that group good without a gauge. You shoot and watch what your point of impact does on the target.

    The more you shoot the more you see what that pellet hits like. But a chrony is nice to get hard data with. And the cool thing about it all is you get to have fun shooting while your actually collecting important data. Then compare chrony readings to target data and you should end up with a very accurate shooting pcp air gun.

  3. I own 5-6 multi pumpers, and I Like that type of airgun a lot. I like not having to worry about CO2 12 or 88 gram cans. Where I live, I can’t order them online because 1. nobody will ship them by air, and 2. nobody would ship them to my Post Office box anyway. I like multi pumpers because they are easy to shoot well due to no recoil. They are usually pretty quiet. Accuracy can be quite good too. I like springers too, but can’t get mine to match my multi pumps regularly. And, springers are generally loud. I do have a couple of CO2 rifles and some pistols too. My CO2 rifles are easy to shoot well, and one is whisper quiet, which I really appreciate. I am considering buying myself a Crosman Maximus and a hand pump for it also. Can’t wait until Tom does one of his great multi part reviews!!

    • Birdmove
      You guys are all talking about the multi pump guns.

      Have your evere tryed putting a Crosman steel breech on a Crosman 1377 or 1322 with a Benjamin Discovery barrel. And then add a Crosman 1399 skelton stock. I have had several of these guns I put together in .177 and .22 caliber. Then throw on a dot sight or a scope.

      They make for a very light weight gun that is very accurate and makes adequate power. Oh and they are fairly quiet. I have done alot of pesting with those types of guns.

      And my girls when they were younger always liked to shoot them because they were so easy to hold.

  4. Gunfun1, I have both a 1322 and a 1377 with steel breeches, and the skeleton stock. They still have the stock barrels on them though. The Discovery barrel will bolt right on? I have used the 1322 with a red led flashlight for night ratting on a small scale. I also have a Crosman Custom Shop 2400KT CO2 carbine in .177. I recently put a TKO muzzle brake on it, and it is super quiet and accurate.

    • Birdmove
      Yep will bolt right on. Probably a 10 minute job at the most.

      The hardest part of it all is you have to drill the front barrel support out so the outside barrel diameter will slip through. They step the front of the factory 1322/77 barrels diameter down where it fits in that from plastic piece that has the front sight post on it. So when you drill it out. Choose a drill that will give a snug fit as your slipping the new Discovery barrel in. I use a little light oil on the barrel as I’m slipping it in. Then just wipe it of when you got the barrel in the breech and locked down.

  5. B.B.,

    Good article and a timely one as I am one of those getting ready to take the “plunge” into the “Dark Side”.

    One of my concerns was/is that the on board gauges seem small and not “precise” in their increments. I think, why not digital? At any rate, I went to PA and blew up the picture for a Marauder gauge. 8 increments per 1000 psi. That figures out to 125 if the needle lands on a line. If one were to go between the lines, this would allow readings down to 62.5 psi increments. Perhaps that is close enough. To me though, once the power curve is figured out, it still seems like guess work to a degree. Maybe good enough for target, but not for hunting as you don’t want the first shot landing high due to an off curve high fill.

    What about a hose with a more precise gauge to use as a pressure checker for the on board tank? Or, an inline gauge between the filler tank and the gun tank that would read gun’s pressure once the filler tank valve is closed. I still need to decide tank and hose options, so something like this may already exist.

    Anyways,….good article. Chris

    • Chris

      An overfill will give you slow shots, not faster .
      Trying to milk it out for that very last shot of a fill is going to bite you .
      I was out shooting a few years ago, and thought I had something wrong . The gun was running very weak . After a dozen or so shots, I checked the gage and found that I had more pressure left than I started with .
      Was back out the next day with a fresh fill (room temperature) and a infrared thermometer .I watched the gage and kept checking the thermometer as the gun warmed up (warm day) .
      Point….You gonna get the gun warmer outside, don’t fill so high .


    • Chris, the gauge (and that spelling seems correct for the type with a needle and an indicator) on your rifle is likely to be small and hard to read well. On your air tank, you typically have a bigger liquid filled gauge that can read more precisely. I hardly look at my Marauder’s gauge, but after 25 shots, I will carefully fill it to about 3,000.based on the indication of the tank’s gauge. Watch that needle climb, and throttle the valve to hit a point about 100 psi higher than you like. Close the tank fill valve, and then open the bleed valve to release the pressure in the fill tube before you release the quick disconnect. You typically lose a little pressure in doing so.

      As Tom says, you need to get these parameters established with a chronograph, noting the best fill pressure and the number of shots you can get in the power band. When the gun’s pressure drops to a certain level, so will your POI. Counting shots is the way most shooters know when to re-fill.

      • Excellent advice. I’ll add something to simplify it even further:

        Once you test the gun with a chronograph and understand how it shoots, you will find that you fill it off the gauge on the fill device (always bigger and easier to read, and usually more accurate too), and then shoot it for a specific number off shots, and then refill again. You will not be using the gauge on the gun as you shoot, and hardly at all.

        I find that I only use the gauge on my PCPs for a quick visual check to verify that the gun has not leaked down while sitting in the safe between uses. If I ever doubt where I am in the fill or lose track of how many shots I have taken (hard to do with guns with a mag, but easier on a single shot) I simply refill and reset the gun, as well as the count in my mind.

      • JerryC
        Yes your right, (gauge) is the correct spelling for a needle and numbers.

        A (gage) is a hard gage as we call them at work. It could be a plug gage which is a precision dowel pin to measure a inside diameter. Or it could be something you put the part in that could measure hole locations or notches in a part.

        I remember a while back somebody was calling a dail gauge a gage and I was going to say something and forgot.

    • Chris USA,

      I never pay attention to the gauge in the gun. They’re too small and often inaccurate.

      Pay attention to the larger gauge on your hand pump or tank.

      Once you have figured out the ideal power curve for your gun fill to the ideal pressure. Filling while watching the large gauge on your fill apparatus will easily allow you to avoid overfilling.

      Once you have figured out the ideal power curve for your gun you will also know how many shots you will get in the “sweet spot” of YOUR power curve. Then keep track of your shots to know when to refill. With a multi-shot airgun it’s easier. If I have 10 round magazines and my gun gets 50 good shots then I know when I’ve shot the 5th magazine it’s time to refill.

      For the example above, I carry 5 loaded magazines into the field. Once they are empty I know my gun needs to be refilled.


    • Chris USA
      Me and Buldawg had exactly this same conversation.

      I don’t worry about hitting the exact fill pressure I chose for a particular pcp gun. The gauge on the gun is for reference. The fill pressure I chose I know that if I fill a 100 or so psi higher that the gun will still POI (point of impact) right. And same at the ending pressure that I determined. The gauge on the gun is only for reference. I know that I can shoot a 100 or so psi lower than my chosen ending pressure and again the gun will still POI and group good.

      Matter of fact I messed my Mrod gauge up over the weekend. I had just filled the gun up and set the gun on my shooting table. It was warm in the breezway and there is a bunch of big windows in it. It’s actually like a sun room if you will. But I went out and road the 4 wheeler’s with the kids for about a hour and a half. Came back and the needle was pegged straight down. Maybe something like at 4500 psi if there was still numbers there. Well first thing I did was freak out of course with that much pressure in the gun. So I shot it and the gun wasn’t valve locked. So I just started shooting. What I found is the gauge didn’t move correctly going down. So here’s another important shooting tip with a pcp gun. I continued shooting counting off the usual number of good shots I get from a fill till I see POI changing. Guess what the gauge moved down but was still in the red at about 3500 psi. So next important thing. I hooked up to the Shoebox and when the fill valve clicked open on the gun I was at my normal 2500 psi low pressure or ending fill then I topped the gun off to my high fill pressure by the gauge on the Shoebox. Well guess what the guns gauge was in another place.

      But see what writing info down about a pcp gun does for you. I had a low and high fill pressure wrote down from the Shoebox and my gun. And also the usable shots I get per fill.

      But here is the gauge I got for a replacement on the Mrod. It’s the same diameter and will screw right into the Mrod in the same factory place. But if you notice. It goes to 6,000psi. So the markings are for sure smaller. But back to what we were talking about. I don’t care how small the gauge or spacing is. It’s just a reference point after I established my guns perimeters.


      • Speaking of over charging, I have a M Rod (25 caliber) myself, I use a large steel bottle like the ones you see in welding shops to fill mine. It’s been (2) years and it just getting down to the point of refilling. It’s rated for 6000 psi. I had it filled with air the first time, next time it will be with nitrogen. I have a regulator that I can set to any pressure that I desire. One day I decided to pressure check my carbon tank, I filled it with water and tested it to 5000 psi and it checked out fine. My mistake was not resetting it to my charge pressure of 3000 psi when finished. I would like to have had a selfie when I realized what I had done. Probably would have been good for few laughs.
        But back to the results, I decided to just shoot till the pressure was relieved, I was surprised that it would actually fire seeing the pressure was so great. As expected the shots were weak till it was back to normal pressures and it did ruin the gauge, it would leak down if left stored with pressure. I replaced the gauge.
        . But I was so impressed with the quality that was engineered into the gun.

        Kudos to Benjamin!

        Now I wouldn’t recommend doing that, I’m just stating that Benjamin’s products seem to be well engineered.
        . It appears there’s plenty of room for experimenting to find that sweet spot.
        . I hope my experience helps others feel comfortable about the limitations of the Benjamin Marauder.

        • Mac
          Sounds exactly like the results I got when I left my Marauder in the direct sun after filling.

          My gauge doesn’t work right and its leaking down. Got the new gauge today. Going to put it on tonight and fill it up and see if it holds pressure over night.

          Hope it just messed the gauge up internally and I don’t have to put new o-rings in the gun. I will know tomorrow though. Fingers crossed that it’s the old gauge causing the leak down.

          I’ll post results tomorrow or the weekend.

            • Reb
              And I already decided if I have to take it apart to replace o-rings. I’m going to modify the valve like I done on my gen1 .25 caliber Marauder that had the double resivoir on it that Lloyd Sikes made for me. It was a powerhouse and the double tube still allowed me 23 consistent shots. It was only getting 11 shots per fill with just the single factory resivoir. So you know I had the power heavy on it. Let’s just say that the 31 grain Barracudas was right up there with standard velocity .22 rimfire rounds. Yes it used air. Yes it t rock’n rolled. So maybe I do need to go inside this one. 🙂

          • GUNFUN1
            I have to say I’ve never had to deal with higher pressures in my gun because of temp changes but I have noticed changes in my bulk tank for that reason. That’s why next time I’ll fill it with nitrogen, it’s a more stable gas when exposed to temp changes and there’s no chance of moisture. I think the price to fill is about the same. As I stated in my other post, the tank can be filled to 6000psi and regulated to my charge pressure. With a tank lasting at least (2) years and being so convenient over a pump, I’ll gladly pay a little extra for the nitrogen.
            I do enjoy my Marauder it’s accurate, quiet and cheap to shoot. Plus with the cost of 22 ammo being hard to find for so long and now kinda expensive when you do find it.

            I have to say it’s more enjoyable to plink with than any of my 22’s.
            My back yard allows me 110 yards of pellet heaven. Not to mention the cooperation of the crawfish for those little crawdad chimneys. They make the greatest targets. Even at 90 to 100 yards the 25 caliber Marauder turns them into dust clouds on impact. Always puts a smile on my face!

            And thanks BB, I do enjoy the blog.

            • Mac
              Yep that checked into nitrogen sometime back and decided on the Shoebox for different reasons.

              But yep where I live know I have 175 yards to a tree line then about the same to another one and so on for probably over a 1000 yards. No neighbor’s for along ways.

              But yep those .25 Mrods are amazing guns. The one I have right now has taken many starlings out to a100 yards and more. It’s probably more accurate than some of my .22 rimfire rifles. And of course much more quiet.

              Yes the them .25 Marauders will definitely put a smile on your face. 🙂

          • Just a update.

            New gauge in the Marauder yesterday and filled to start psi. I Let it sit overnight and gun is holding pressure. The gauge needle is setting dead on to what I filled the gun to yesterday.

            So glad of that. Well I guess no hopping up the Mrod internally yet. But that’s ok it’s shooting great as is with the JSB 33.95 grain pellets. But just glad it’s holding air. I hate a pcp that leaks down.

  6. Off topic, but have you or will you consider taking all of your Airgun Letter articles and combining them into a book? I know that it would sell. Some of the articles may be out of date, but would still be great reading for those of us that follow your writings.

  7. Good reading again, Tom. I’d like to see you report on various chronographs, and the nuances of using them. They seem to be a big key to the performance of a gun – you report on results frequently, and I’d like to know more about their features, usage, etc.

      • Tom, I meant that you report velocity results frequently. I have had two chronographs, and use them, but I need to be careful in their setup, it is easy to get “incorrect” readings. Lighting is always a factor, and it can be frustrating to get everything setup properly. I’m thinking you know about these things, and that there are new options for these devices that are interesting. I’ve had two myself, and the newer one is better in most ways, especially in that it logs results to my smartphone.

        • JerryC
          Me and Buldawg have been trying to figure out velocity differences between our chronys. He lives about 3 states away from me. He has got some air guns from me. His readings are usually slower by about 75-100fps than my readings with the same pellets used.

          Got to be a reason why. We are starting to think it’s air density. In other words how thick the air is outside I guess I will call it.

          But probably what your talking about is a little different condition that what we have going on. But yes that would be a interesting subject too.

  8. You described the maximum usefull pressure and gave numbers of 2800 to 3100psi. I have a Benjamin pcp that I do not fill past 3000psi on either the gun or the pump gauge. They read really close. It is my understanding that this is the maximum safe pressure of the equipment. Because the first shot at this pressure is in the effective power band, should the resivior be filled further to find the top effective pressure?

    • Gopher,

      As BB says, you have to do what you feel is safe, and you have to accept full responsibility for any decision to go over the rated pressure.

      That said, I will share an important fact, along with what I did with mine for quite a while.

      The first is the impact of temperature change on air pressure. If a gun is filled to 3000 psi “cold” – say outdoor shooting in winter – and then the temperature of the gun rises about 40 degrees F – like if brought indoors after the cold fill – then the pressure will rise by about 8%. That would put it at about 3250 psi. The gun was designed to withstand this with no problem, so there is a safety factor. Whether or not to go into that range is up to you.

      Several years ago I had my Marauder tuned to shoot best from a 3200 psi fill (it is now regulated, so I don’t fill that high any more). After shooting, I refilled to that level and put the gun in the safe. I used it this way for probably two years with no ill effect to the gun – of course I never allowed it see any big temperature swings while in this state, but it spent a long time stored at 3200 psi. While tuning it, there were a few fills that went up to about 3300 to see where I really was, but I had no intent of filling that high on an ongoing basis.

      Bottom line, I personally believe filling it a little higher to see your full shot string is of minimal risk. But you own both the choice and that risk.

      • Alan
        That is right. I went through all that to back when I got my first Benjamin Discovery when they came out.

        Inside and outside temperature will change the guns psi. Especially if you leave it set in direct sun light or if out in real cold weather for a long ng period of time. (Read my comment above to Chris USA about what just happened with my Mrod over the weekend).

        But what I did was shoot the Discovery out in those conditions at my target and chronyed the gun also. You wouldn’t believe all the targets I saved with all kinds of info wrote on them when I got that first pcp.

        Documenting pcp performance is a must if you want to get the most from your gun. And don’t ever think two of the same guns will have the same fill or ending pressure or should I say power curve.

        I think I had like 6 Mrods throughout time. A couple Discovery’s. A few Crosman 1720T’s and a Bengamin Prod. A few Talon SS’s. And also a couple FX Monsoons (talk about a gun that needs fill pressure’s established). Oh and a couple of 2240 HPA hi-pac converted guns with Discovery barrels. And the list goes on.

        But what’s important each individual gun needs tested and documented. They all have their on character.

    • Gopher,

      As with most consumer goods, there is a safety margin built in. Gunfun1 mentioned that his gauge pegged at 4500 when getting warmed by the sun. You might ask the Manufacturer what they test their tanks to. As long as you don’t get stupid, I would think that 3500 would be safe and most likely be too high on your power curve anyways.

  9. B.B.,

    “Fill with many pumps and then [GET] exhaust all at once”! Well, age might have a lot to do with it.

    Your sage advice to “learn/know your gun” applies to all of them, doesn’t it? :^) As I read today’s report, I thought of the fellow who uses, with success, a Sheridan Blue Streak for FT that you described and pictured a couple years back. That is a guy who must know his gun exceptionally well.


    • Michael
      I was going to bring that up.

      There is nothing more fun than using different number of pumps for different distances and not having to use hold overs. Just put the center of the reticle on the target and let the velocity do the rest.

      If nobody has ever tryed it they should. That is fun shooting.

      And not to say Ron Robison ain’t good. Because obviously he is. But I’m sure he’s got a cheat sheet established for how many pumps is needed at what distance.

      You know what the trick to making something look easy when you show up at a event or match. A lot of hard work and testing and documenting at home. There’s people that can just naturally do things good. But they still have a good understanding of how something works and what needs to be done.

      What I’m trying to say is yes Ron Robinson is a very smart guy I’m willing to bet on that.

      • Ron Robinson is not only a good shot but he has the trophies to prove the point.

        Ron is very knowledgeable about many, many airguns. He’s also an accomplished hunter with airguns. He’s written 4 books about airguns (The Manic Compressive, Airgun Hunting and Sport, A Sporting Proposition, and Airgun Chronicles).

        For those that like to tinker with and modify airguns you should have Ron’s books in your library.


      • GF1:

        For different numbers of pumps for distance, I made a range card for my 1377 (modified to 18” barrel, steel breech, and a 1399 shoulder stock) with a 3-9 scope. I believe I learned this technique here (from you?).

        Draw a horizontal line on a sheet of paper. I use an 8 ½ by 11 sheet of paper turned to landscape (sideways) and draw a line down the center. I put a witness mark every inch to use an aiming point. Make several copies of the sheet. I start with 3 pumps aimed at my left mark. Then pump 4 times for the next mark and so one until I end with 8 pumps. I set the first target at 10 yards, the next at 15 yards, until I worked up to 30 yards (max for my back yard.) I can use the data from the various distances to create a range card that can give me the number of pumps for the distance to be exactly on the aim point (if I do my part). I can also use the data to know the hold over/under for a given number of pumps at a given distance.

        Please note that my carbine is sighted in at 20 yards with JSB RS 7.33 grain pellets with 5 pumps. A different range card would have to be determined for each different pellet used. My rifle is not picky, so I have range cards for JSB RS, RWS Basic (out to 25), and several others.

        I hope this helps others. I know it helped me to increase my accuracy with my 1377. Thanks to the person who posted the original tip!


        • Jim
          It could of been me. I know I have talked about it in the past. And that is exactly how I do it.

          But yes that is very accurate and fun way to shoot a pump gun. You don’t know how many feild mice I have taken in barns with a 1377 with a steel breech and Discovery barrel with the 1399 stock and a red dot sight. As long as you map out your distances like you said and are good at determining your distances that is a deadly combination for sure. And what’s cool about it. At closer distances you don’t need as much power. So at the closer distances the less pumps you determined for your POI works out for the energy you need. More pumps for longer distances for your POI and you then have the extra energy. Definitely a fun combination to experiment with. But glad you tryed it and it worked out for you.

          • GF1,

            I’m amazed at how accurate the 1377 is, both before and after I added the longer barrel and shoulder stock. It’s much more accurate than I am. I keep saying that I’m going get a 1322 and do the same mods to it. But my wife says she is going to beat me over the head with the next gun I get. I’m still wearing a football helmet to bed after I got my AT44 and she told me to go ahead and but it as a late Christmas present. (I don’t think that she know what it cost when she said that. LOL)


            • Jim
              Haha yes I know what you mean about the football helmet.

              But I’ll tell you it is amazing how accurate that 1322/77 combination is. And they are relatively cheap and easy to biuld also.

              If you do biuld another one let us know how it turns out. But just don’t let your wife find out ok.

                • Chris USA
                  You should.

                  1377/22 around $55.

                  Steel breech $30.

                  1399 stock $30.

                  Discovery barrel from Crosman about $20 if I remember right.

                  A little 4 magnification fixed power scope $50 or a red dot sight sight for about the same price.

                  Yep fun guns. Get you one. 🙂

                  • GF1,

                    Mmmmmm? I believe it was you, when I got the 880 for dart and arrow testing, that you said….” hey,…you are spending all your PCP money”,….was it not?

                    The ol’ wallet has a bottom. ‘Bout to go “diving” as it is. Sounds like a lot of fun though.

                    • Chris USA
                      Hey you just brought up that it’s got you thinking about the 1322/77 combo.

                      I’m just giving you a little nudge.

                  • GF1,

                    I will have to remember to order my next barrel from Crosman. The Crosman price is about 1/2 what I paid. I did get a good deal on the 1399 stock on eBay. The 1377 and the steel breech kit came from PA.

                    I’m trying to talk myself into not ordering a 1322. I don’t believe I’m succeeding.



                    • Jim
                      Go to the Crosman website and pull up the parts diagram for the Discovery. Get the barrel part number for the caliber you want.

                      Then give Crosman a call and give them the part number. They will give you a price. But if you don’t have the part number there’s no sense in calling. They won’t look up part numbers for you. But if you got a hundred different part numbers they will gladly tell you price and availability.

                      Also there’s usually a 2 week lead time on the barrels. They crown them upon shipping. So just a little warning if your wanting the barrel now.

                      And then if your trying to talk yourself out of a 1322 well then you shouldn’t be talking to me. Because I’m going to tell you go for it and get that 1322.

              • I’m planning to put the stock from my 2240 over to the 1322 I’m building now, gotta get a couple barrels before I can do much else.
                What’s the longest barrel available through Crosman? 24″ would be nice and 26″ even nicer

                • Reb
                  The Discovery barrel is 24″ if I remember right without one setting in front end f me.

                  The Discovery barrel works out real nice on the 1322/77’s in .22 or .177 cal. Had both caliber Disco barrels on a 1300 platform.

            • Jim,

              Real cute on the comment. They,… (wives),.. have their pluses and minuses. I think I do remember, you speak rather fondly of yours,……still,…the football helmet,……good idea. 😉 Got to live long enough to get her talked into to your “next” one,….heh?

  10. Something else that I want to bring up is the sound of the report the gun makes in relation to fill pressure.

    Usually at the full fill pressure if you go above your guns power curve. The gun will not be as loud as normal when tou shoot because the the extra fill pressure will make it harder to open the valve. But as you start comming on to the power curve the shot will get louder and stay at that sound for the amount of good shots you get. Then when the gun starts falling off the power curve the gun will start getting quieter. Which means there is less pressure to the valve so the air is released differently to the barrel. Alot of people call that shot sound fluttering and maybe even more commonly known as farting yes I just said the gun will sound like it’s farting once you go below the power curve.

    So not only establishing begining and ending pressure and counting shots and watching POI. But also listening to what the gun sounds like when you shoot. All I can say is the more you shoot your pcp the more you will recognize the sound change and the other things also.

    Shoot have fun and learn your gun. Like I have said before. Listen to your gun. It will tell you a story.

  11. BB:

    Great blog!

    You mentioned the Benjamin 700 series as being guns that can be pumped up then shot several times before having to pump again. Although WAY out of my price range, how about the FX Independence and Indy? These two guns can be pumped up, then shot several times before having to be pumped up again.

    Also, I believe that I read about someone converting modern 392 or 397 guns to retain air for multi shots without additional pumps (or maybe only one or two pumps between shot.


      • BB:

        You know the market much better than I ever will so if you say that there is market for this type of air rifle in the $500 – $600, I’m sure that we will see you reporting on one at the next shot show. For me, the gun would have to be in the $350 – $400 range in order to compete with a Maximus or Discovery with a hand pump, even if sold as a survival gun.

        Way off topic, have you set the dates for the 2015 Texas Airgun Show? If the dates are known, I can get it on the vacation calendar at work.



          • Glad we have a date to start saving for now!
            Keep us in the know for sure
            I’ve got a couple BB guns ready so far but I’ll be placing a couple parts orders outta this next check and see what else I can get ready in time.
            I do plan to be there again this year and it should cost a lot less because my sister has now moved to the Metroplex. Only thing is that the time of month is crucial to account balance for me, and probably many others on a fixed monthly income.
            It could have a major positive impact by moving the date set much closer to the first of either month.
            I feel confident about this recommendation and submit it for approval.


          • BB:

            Thank you for the info. I’ll put in for vacation on Friday, August 26. I’m sorry to here that the venue has changed. Those were nice folks running the range last year.


        • Jim
          The gun is a Benjamin 392 ACP (Air Conserving Pumper).

          Steve Woodward is who designed the conversion. Yes you only need 3 pumps to maintain full velocity after first pumping the gun up 8 times.

          I think I that is a very cool gun.

          Oh and the FX Independence is also a cool gun.

  12. Yes, very illuminating about the physics of the power band in pcps. And the power band is an essential piece of information because it would get very frustrating for your groups to come apart if you’re off the band. And I suspect that the easy power adjustment to the Air Force guns would play hell with the power band, as I understand the physics. This would be an argument for the Marauder power adjustment which is designed for very occasional tuning.

    Chris, I really recommend Samurai as a war memoir. Sakai was sort of a Japanese Kilroy was here. He apparently participated in shooting down the early American war hero Colin Kelly over the Philippines. And he confirms that Kelly did not fly his B17 into a Japanese ship but he did go down with his plane to keep it flying long enough for his crew to bail out. Sakai’s description of the invasion of Guadalcanal is calculated to fill every American with pride. Sakai said that a gray armada stretched over the horizon, and he had never seen anything like it. Japanese landings had a few ships and individuals hand carrying supplies. This was before Admiral Fletcher withdrew his ships prematurely but it was a foreshadowing of what was to come.

    Anyway, after almost getting shot down by Avenger torpedo planes, Sakai woke up right before hitting the water and leveled his plane. He must be one of the few people to survive a head wound from a .50 caliber round. It couldn’t have been the round itself and must have been fragments. After fixing this as best he could, he adjusted his fuel consumption and flew for hours back to his home base, partly upside down and fighting to keep from falling asleep. The surgery on his eye afterwards was done without anaesthetic for some reason and lasted for six hours. It would make Draeger’s root canal look trivial by comparison. Then, because of the pilot shortage, he was back in the air as a one-eye pilot and even holding his own against superior American fighters despite his lack of depth perception. He even managed to survive a kamikaze mission because his group lost its way and he didn’t see the point of crashing into the empty ocean. After the war, he was astounded that as he says that American pilots who had “come under his guns” actually offered him friendship. And what do you know but later in life, he found himself as a an invited guest on an F-16. That is certainly a long way from a Zero fighter, so you never know how things will work out in the end.

    As for the Japanese people, they are quite paradoxical. There is a missionary in China during WWII named Gladys Alyward who wrote about the Japanese in a memoir. Incidentally, she must have been in very similar circumstances as Edith who I believe came from a missionary family in China. Anyway, Gladys wrote that she could never reconcile the incredibly kind and friendly people she met in Japan before the war with the barbaric behavior of their soldiers abroad. Neither one was fake. They just seemed to be different aspects of the same people. Medal of Honor winner Gregory Boyington says the same in his memoir. Getting shot down and imprisoned by the Japanese was something of a redemption for him. In particular, it dried him out of alcohol which was taking a severe toll. And he formed very deep friendships, especially with an old Japanese lady who smuggled him food at considerable risk to herself.

    No doubt the Japanese know how to work. But my brother, in his experience of working for them says that they are highly inefficient. Between their shame culture and their intricate hierarchy a lot of time gets wasted. Their work ethic covered for a lot of that during their remarkable post-war recovery. But they have foundered through an inability to cut their losses in a capitalist system and they are now quadrillions of yen in debt. Even worse, they have something like the lowest birth rate in the world and without some significant change could essentially disappear within a few decades.

    But I have to agree with you about their food which I have newly come to appreciate. While America was founded on the premise of creating something new, you have to hand it to these old cultures. They have great accumulated knowledge of how to have a good time. There I was in a hot bath in the early morning at a resort. The walls were glass, and they overlooked snow covered mountains that were turning pink in the rising sun. Physically, mentally, and emotionally it was mighty fine, and then on to the great food. Incidentally, it is a fact that the Japanese are just about the longest-lived people in the world due to their extremely healthy diet. When my Dad stayed with a family for a few weeks, he lost something like 20 pounds while eating three full meals a day. If I could just get on a Japanese diet, my problems would probably all be solved.

    As for what the Japanese have given us in shooting, I believe that they were instrumental in airsoft because of the restrictions imposed by the WWII surrender. Such was my mindset that had I not used airsoft as a transition, I might never have made the jump to pellet guns and firearms. And airsoft continues to be relevant. I read about some Japanese champion in airsoft action shooting who came over to the U.S., practiced for a month, and then won a whole bunch of action pistol shooting awards with firearms. Also, you may not remember Wayne, one of our illustrious bloggers who learned about airguns and then went on to become some kind of field target champion. He was very fond of the Japanese Howa bolt action rifle which he claimed could do marvelous things. And I myself am quite intrigued by their Type 89 assault rifle. It looks like quite an effective piston design. But because of restrictions on arms sales imposed by the WWII surrender, there is very little information about it.


  13. To all
    This is indeed a very informational and intriguing report and for the most part I agree 100% with all that has been said concerning fill pressure’s and powerbands as well as learning your guns own characteristics.

    Like GF1 and others have said temperature will play with your mind if you obsess over the gauge on the guns reading a different pressure when filled inside/outside and then shot in a different environment so that there is a large difference in the two temps. I like GF1 use my large liquid filled gauges on my shoebox and field bottles to fill to my desired pressure and only use the gauge on the guns as a reference ( fortunately my guns gauges are for the most part the same reading as my liquid filled gauges ). I use shot count as my main stopping point to fill at since I shoot FT every month and I am more concerned about not missing due to the last shot being the one that just came off the powerband then what the guns gauge reads as a fill point.

    I also fill some of my guns to 200 psi above the advertised max fill pressure so as to get a few extra shots on the power curve out of them since I see it has not been discussed here that some guns such as the Mrods have three adjustments to allow the moving of the powerband up or down in the fill range to ease with filling by hand versus a compressor. My 177 Mrod is tuned to get 50 shots with JSB 10.34s at a starting fill of 3200 psi down to 2200 psi with a starting velocity of 920 fps and end velocity of 900 fps which allows me to shoot an entire match on one fill.

    I have been reading quite a bit on other forums about the max velocity and efficiency that is possible out of any PCP guns dealing mainly with fill pressures and volumes in order to try to determine the max velocity that can be achieved from a PCP gun regarding the physics of air and pressures along with efficiency of the air used. It is also helping determine how to design as efficient of a PCP as possible and has at this time proven that after 75% of the barrels length has been covered by the pellet there is very little to no gains achieved by the valve still being open releasing air into the barrel so the key in tuning is to find that sweet spot where the valves dwell time and air pressure are working at its most efficient point to gain the highest velocity and shot court possible for a given amount of air used. The test gun to this point has achieved 1745 fps shooting a 10.2 grain 177 caliber pellet/slug with a barrel of 24 inches and 4500 psi with a 26.5cc air reservoir in a full dump model test gun so its using 26.5cc of 4500 psi air to push a 177 caliber pellet ( custom made aluminum ) to 1745 fps or almost Mach 1.5 and hoping to achieve Mach 2 before the test is done.

    The main thing I take away from all this is regardless of fill pressure or gauge reading is shooting your particular gun to learn its likes an dislike and characteristics as well as how one adjustment ( if it has the capabilities ) changes the way it performs versus another change is what important and is what makes this sport/hobby so much fun. There is always something new to learn or gain from trying new things to improve what we have.

    I would like to second JerryC’s and GF1’s request for a report on the best/proper way to use a chrony for or testing purpose since like GF1 said we have had guns that were shot over his chrony and mine with a large variances in readings and have not yet come up with a viable reason as to why they read 100 or more fps different with the same guns.


    • BD76,

      1745! Wow! Is that you or some of the testing that you been reading? Impressive to say the least. Good advice in your comment. You are a max. tuner, so your comments always hold a lot of interest for me and others interested in doing the same. Also, for some reason, your comment is much easier to read. Punctuation, pauses and paragraphs work. Don’t know what you changed, but keep it up. Take care, Chris

        • BD76,

          Thanks,….saved to favorites,…along with many others I need to explore more. Very interesting testing though. THAT is what makes new products and breaks old thinking. I like it. Keep us posted for those of us that do not get “around” as much. Chris

      • Chris,USA
        He is now talking about going to a longer barrel and larger air volume as well as bigger pellet to get to Mach 2 or over 2200 fps from just air. Very interesting reading for sure.


    • BD
      Resivoir on the gun is something I mentioned when BB said he was going to do this report.

      I had that double tube resivoir on one of my .25 caliber gen1 Marauders I had. Obviously the gun held more compressed air. I had that gun way modded out and it was making crazy power. But I was only getting 11 shots per fill from 3200 down to 2500 psi and velocity and POI dropped off fast. Something I don’t like in a pcp gun. I put the double resivoir on it that Lloyd Sikes made me. What that did was upped my shot count to about 23 shots per fill.

      But here is something else to note. If I only took 11 shots after putting the double tube resivoir on. The gun was still making the velocity I wanted but now I would only use 3200 down to 2900 psi of air for those 11 shots and got a much closer velocity spread that held. And then if I continued shooting to shoot 23 again my velocity was stable. After that 23 shot then the velocity would start falling off. But it was a gradual drop in velocity.

      That’s like my Talon SS and the .25 Mrod. The Mrod as shipped from the factory doesn’t hold as much air as the Talon SS. And by that I mean volume of air. So I do believe that attributes to why the Talon SS will get more shots per fill. Well and the rest of the combination as its set up on each gun.

      But yes it all boils down to testing, documenting and tunning. But when you get them right it sure is nice how well they shoot.

      • GF1
        Yea the reservoir is exactly why I am building that 25 Mrod with the 500cc bottle on it so I can get the power and shot count out of it to have the best of b0th worlds so to speak.

        My new barrel is done and just waiting on the valve to be completed as the lathe they used for the valves had a spindle failure and is what slowed the replacement of my bad valve and possibly is why the original valve was not made true to start with, not sure but should have both parts in the mail next week so then I can reassemble it and get the tuning started just in time for spring. Yippee. Hoping for a 70 fpe gun with 40 plus shots or better and the capability to turn it up to 100fpe for max power shots and with the new custom barrel be capable of 1 inch groups at 100 plus yards with ease if I do my part. LOL.
        Got to practice my breathing and controlling my heart beat for sure.

        Your talon with over twice the air volume and smaller pellet should get at least twice as many shot as the 25 if not more than twice since the air usage from 22 to 25 is much greater than from 177 to 22 is for any given gun. of course if you have the talon tuned hotter than the 25 then that will affect shot count as well.

        It is indeed all about testing and documenting to get the gun to shoot the way you want and then enjoy them as much as possible.


    • BD,

      I will do it for you. The difference in velocities is something I can address, as well as some other things. I told JerryC that I owned 2 chronographs, but the truth is, I had one more. It was one of those Brit ones that you attach to the muzzle of the gun.

      I should be able to write a pretty good blog.


      • BB
        I do appreciate the willingness to do a report on the proper/best way to use a chrony as I know you have your plate full all the time but I as well as other feel it is something that can be as well as is not fully understood as to just how to go about obtaining correct and accurate results. I know I get repeatable result with my guns but unsure if they are indeed correct or accurate.

        I know I told you about the issue me and GF1 have with reading between our chrony’s reading different with the same guns and not being able to determine a viable reason other than air density in our respective locations. It may be that we are not testing the same or correctly to obtain proper results and should be a good report for all to learn from as well.

        I have seen those barrel attached chrony’s and would be interested in the difference/ accuracy/ repeatability of that style as well.

        Thank you and look forward to it in the future.


  14. Matt61,

    Impressive,..as usual. No war buff, of any kind, or firearms expert for that matter. So,…I will leave those up to you. I can see the Japanese culture as you described. Which may explain the long hours in order to make up for other things. “Paradox”,..as you said,…fits well. As for the food,….Sushi or Sashimi grade sea food is the toughest challenge. Frozen is your friend, but texture suffers some. The rest is pretty easy especially if you have any ethnic markets where you live. I can roll a pretty mean sushi roll! 🙂 Then the Wasabi w/soy!,….yum, yum,…. I like it hot! Chop sticks?,…… like a pro. Those differ as well from culture to culture. Visual presentation is important, as well as “order”, as you said, in (all) things. Cool on the airsoft,…that makes perfect sense.

    Thanks again for the added insight,…… Chris

  15. Way off topic, but I need some advice on iron sights. I’m a frequent reader, but I rarely post. I know BB has written about iron sights in some past blogs, but I wondering about specific setups for specific targets. I just acquired an HW30s, which comes with six front sight inserts. And it has four rear sight notch selections. Six time four gives 24 combinations to test, so I am wondering if there are any “standard” configurations, or if anyone here has a favorite setup for a particular type of target. Also, I don’t even know what some of these sight shapes are called. Here’s what I call them:

    1– Tapered post (I think BB calls this a perlkorn. It was mounted in the gun on delivery, so I guess this is a sort of universal application. I have seen these before, and I haven’t been able to get very good results, I think because my old eyes can’t see the tip of the taper very well.
    2– Wide square post. This looks like it should be paired with the wide square rear notch. Maybe best for short range?
    3– Narrow square post. Looks like it should work with the narrow rear notch. Maybe this is intended for longer ranges?
    4– “Doughnut” ring with a large hole in the center. I tried it at 7 yards with some Gamo printed targets that have a white bull in the center of a black bull. Seems to “flash” white when you are on target, which is nice. But it is kind of like a dot sight with a large dot, it doesn’t feel very precise. All of the pellets hit the bull, but I think I could have gotten a smaller group with a post sight. No idea which back sight notch to use with this.
    5– “Bagel” big ring with a small hole in the center. Haven’t tried it, but looks like it would obscure most of the target. Could this be for bench rest, where the rifle isn’t moved once the target is found?
    6– Lollipop” tiny circle on a tiny, spindly stalk. Looks like it will be very precise, if you can see it. I tried this on some scaled-down-to-10 meter metallic silhouette animals. With the “vee” rear notch, I couldn’t see anything. With the “U” rear notch, I shot the best I ever have at that type of target. It might not work in poor light, though (my garage is lit).

    The four rear notches are wide and narrow square, vee, and “U”.

    Does anyone know if there are proper names for the “doughnut,” “bagel,” or “lollipop”? Or which sight combinations are best for bullseye, silhouettes, or hunting? It seems to me that there is more to learning iron sights than I imagined.

    Mike U

  16. “Why don’t they…?”

    I’m an electrical engineer, not mechanical, but I’ll bite. I don’t have a PCP, but if I was to get one, I would want one with a regulator, one where the main tank was filled to say 3000 psi, and the one dumping the air behind the pellet was set to 2000 psi. I wouldn’t care too much about a huge number of shots; I’d be more concerned with all the shots being the same velocity (at least until the main tank dropped below 2000 psi). When I shot Field Target for a while in Florida, there was a gent with such a gun; it was .22 caliber, a custom job, and he said he spent $5000 just for the gun itself. So, I guess that answers the question of “Why don’t they…?” At that price, there wouldn’t be a lot of people lining up to buy them. This guy was retired, and had money to burn (not like I’m jealous or anything =>); he could hit the 1/4″ spinners at 50 yards (from a rest) every time, right from topping the gun off, for like 40 shots (i.e. he could top off, then shoot the match). I guess there’s people out there that would be happy to build me such a gun…but then the $5000 for the gun would be nothing compared to the cost of my divorce…yikes! =)~
    take care & keep up the great work,

    • Thedavemyster
      Welcome to the blog.

      I shoot FT here in central Alabama right now and have several members in our club with up to and exceeding 10k in their guns and scopes and are more than dedicated to the sport as several are former national champions in WFTF class and one is this years national champ in that class.

      I shoot a 177 Mrod in the club in hunter FT class and am by no means any real competition for them but then we are in far different class in terms of the rules they must obey and the rules I must obey but on any given day I have the opportunity to shoot just as good or better than they do so while yes they have far more costly equipment than I do it does not mean that they will always outshoot me. My Mrod being unregulated is tuned to get 50 shots per 3200 psi fill with JSB 10.34 grain pellets shooting at a 20 fps spread of 920 to 900 fps.

      They have been shooting for many more years than I have and is why they have far more costly equipment but does not mean they are guaranteed to always win. I grew up being an underdog in my hobbies and pursuit of enjoyment and found it far more satisfying to buy a used vehicle , bike and now air gun and build and tune to my level of anal perfection and proceed to compete and outrun or outperform the ones that spent far more money than I ever had or could dream of having so buying the best if you don’t understand how to tune and work on it does not guarantee success.

      Success is something that is accomplished thru desire and perseverance and lots of determination, I love when I hear the words it cannot be done as it just inspires me to rise to the occasion and prove you wrong as I have done several times in my life to people who think money buy wins. Granted it helps a whole lot but its not written in stone and nothing is impossible if you want it bad enough.


      • BD,

        I somehow missed this earlier posting by you:
        “My 177 Mrod is tuned to get 50 shots with JSB 10.34s at a starting fill of 3200 psi down to 2200 psi with a starting velocity of 920 fps and end velocity of 900 fps which allows me to shoot an entire match on one fill.”

        That’s cool and impressive; I can see how you could wring some serious accuracy out of such a small velocity spread; and the best thing is that you can shoot a whole match without topping off.

        “…several members in our club with up to and exceeding 10k in their guns and scopes and are more than dedicated to the sport as several are former national champions in WFTF class and one is this year’s national champ in that class.”
        That’s cool to see that level of dedication.

        “I love when I hear the words it cannot be done as it just inspires me to rise to the occasion…”
        I’m with you on that; I once spent six weeks designing a building a very effective boat (i.e. not a toy) out of one sheet of plywood just because someone said it couldn’t be done.

        “…nothing is impossible if you want it bad enough.”

        I concur on that, and thanks again for your info on your 177 Mrod.

        Take care,

        • Dave
          I am very blessed to be a member of an FT club with such talent and dedicated members for sure and am learning by leaps and bounds. I have only been competing since November of 2014 and started with a crosman 40 dollar break barrel and a score of 7/44 so had a lot to learn and realized while a 5k gun would allow me to shoot much better it was not truly necessary for the level I am still at right now.

          I had one of the club member offer me a deal on the Mrod and new it was a huge upgrade to what I started with so grabbed it and started to play with it to finally achieve the tune it has now and so far while still having a long way to go my best score is a 30/44 so for me that is a huge improvement.

          I am in all reality only in competition with myself in that as long as I continue to improve my own scores I am learning and moving forward which is the whole point and fun in doing it to start with.

          The current national champ does indeed have true dedication in that he buys 10k pellets at a time and sorts by head size and weights to be able to shoot pellets that are all as close to exactly the same as possible. Much more than I am willing to do at this time as I am in for the fun and camaraderie.

          I like to hear stories like yours of building that boat because you were told it could not be done ( IE. the person who told you could not or would not do it ) because they don’t have the perseverance to follow thru with something that only serves to inspire and shows us what we can accomplish with our hands and minds.

          I was a GM and Harley master technician for 45 years and when at Harley I was a research and development mechanic at a test facility for 11 years in the durability fleet. I kept the new prototype bikes fixed and running for our test riders to ride 24/7 so I had to diagnosis and repair bikes that had no service manuals or procedures established for the service or repairs. It was my investigations and documentation that allowed the engineers such as yourself to develop those manuals and procedures as well as effect the proper corrections to parts and manufacturing to continue the new Harley products. I had to use my 30 years experience with Cadillac to allow me to test, repair, and document everything I did on the new model Harleys with nothing but my knowledge and some help from engineers to keep the fleet of 30 plus bikes up and running for test of up to 100,000 miles duration.

          I was very instrumental in the development and release of the V-rod water cooled overhead cam Harley in 2001 as well as several other models from 98 to 09 when our test facility was closed and moved to Arizona.

          Man I wish I still had that job as it was like I never worked a day in my life.


        • GF1
          That’s 18.6 to 19.4 fpe so just below the limit of 20 fpe for the hunter FT class and is why I have it tuned to that power for as flat of a trajectory as possible and not exceed the limit.

          I actually turned it down just a bit to increase the shot count so I could shoot the entire matches we normally shoot of 44 to 48 shots. It was shooting 930 to 910 fps for a max of 19.8 fpe but I had to fill at lane 7 to complete the matches plus I have found that the 10.34s tend to lose some accuracy at velocities over 915 to 920 fps. It has helped improve my scores since the first lane or two I was shooting over 920 fps and found that I was missing from a fresh fill for 6 to 8 shots till the velocity dropped below the max 920 its at right now.

          I have done some testing with Shawn’s gun with the o ring buffer in it and have it set at 890 to 900 fps range and found it to be even a bit better for accuracy with still only 50 shots per fill but only using around 850 psi for those shots versus the 1000 psi mine uses. His will actually go over 50 shots but the spread opens up to 20 fps instead of only a 10 fps spread for the last 10 or so shots.

          I would do the same tune on mine but my stroke adjustment screw will not stay where its set so I have it a full stoke and am just using the air screw and hammer spring adjustments. I am debating as to putting in the o ring mod or installing my regulator and light weight hammer in mine to tune for the target velocity of 900 fps and increase shot count to around 70 or 80 most likely plus it will allow me to fix the stroke adjustment screw in the stock hammer when its apart even though I would not be using it with the regulator.

          A lot more than just a yes or no answer but it will help other realize how some fine tuning and simple mods can make big differences.


          • BD
            I couldn’t remember what you said the max was for your FT matches was.

            I do remember when you started tunning for the 10.34’s though. I know back when I had my .177 Mrod and was using the 10.34’s I got much better shooting results when I tuned down to 900 fps.

            You were shooting the 8.4’s at that time weren’t you and then switched over and tuned to the 10.34’s. Or something like that.

            • GF1
              Now you are really asking my brain to work overtime, in all honesty I think I was shooting either 7.9 or 10.5 CPs since I have not shot JSB 8.44s until I got the 124 and then the 300’s. I know I started with the wally world special CPs until you convinced me that they were not as good for accurate shooting and harder on barrels than JSBs or H&Ns are so I guess I only shot the CPs for about a month or two before making the switch.

              I am definitely convinced that the JSBs or AAs and H&Ns are by far the best in my guns of any caliber. Yea the slowing down of the 177s in my Mrod did help a good bit in my FT matches.


              • BD
                I didn’t remember exactly what you was shooting at the time. But I do remember you switching and slowing your .177 10.34’s down. That’s when I was playing with different velocity’s in my .177 Mrod.

                As they fast ain’t always the best when your talking pellets.

                • GF1
                  Yea old habits from our hot rod and dirt bike days are hard to break when as fast as possible was the only way.

                  It most definitely does not apply to air guns and accuracy every time like it did with our cars and bikes.

                  Its just like the motto in the vehicle repair business that states ” slow is fast ” because if you cannot take the time to do it right the first time where will you find the time to do it right the second time.


                    • Reb
                      I used to say the same thing but it never seemed to work very well since if it came back with the same issue I always had to fix it for free.

                      So it was easier to take my time and make sure it was right the first time.


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