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Air Guns Quit worrying about fill pressure!

Quit worrying about fill pressure!

This report covers:

  • My history with fill pressure
  • Ian McKee’s experience
  • shootski
  • Air Arms Shamal
  • How this affects you

Guys, I am in the hospital today, having that kidney stone removed. I may be in the hospital for several days, I won’t know until after the operation is over. Ian McKee is stepping in to help me with guest blogs, though today’s report is mine.

I also want to remind you that July 4th, which is this Thursday, is one of the four holidays I get, so Wednesday’s blog will be up until Friday.

Today I want to talk about one of the silliest things I have seen in the field of precharged pneumatics (PCP) — fill pressure. Fill pressure does not matter, so long as the airgun delivers the power it’s rated for. 

My history with fill pressure

I worked for three years for AirForce Airguns. One of my jobs was technical advisor to the customer. When the Condor first came out in 2004 I personally tested the first 100 rifles and recorded their velocities. All of them had to shoot a .22-caliber Crosman Premier pellet out at 1,200 f.p.s. or faster to be shipped. As I recall, one or two rifles out of that batch did not meet that criterion and we held them back for AirForce owner John McCaslin to examine. Nothing was wrong with them; they simply were not on the power curve at 3,000 psi.

We recorded all the velocities by serial number so people could not claim later than their rifles were defective. Well, nobody ever claimed their rifle didn’t make the velocity we promised. Instead several folks claimed their rifles couldn’t be filled to 3,000 psi and get the promised velocity.

“Yes, but does your rifle shoot Premier pellets at 1,200 f.p.s.?”
“Yes, but it doesn’t start doing it until the tank pressure drops below 2,800 psi.
“How many powerful shots do you typically get?”
“I guess about 20.”
“So you get the velocity we promise and the number of shots we promise.”
“Yes — but not at the 3000 psi you advertise!”

Okay! So you are upset because the Ferrari we sold you does go 230 miles per hour, but it gets 10 miles per gallon instead of the eight we mention in our sales brochure?


Yes, my friends, really!

Ian McKee’s experience

Guest blogger Ian McKee shoots with a friend whose Air Venturi Avenge-X doesn’t like to be filled to 4,350 psi. But when he stops filling at 3,600 psi he gets 30 good shots and can put ten .25-caliber pellets into a one-inch group at 125 yards. The guy was angry because he wasn’t getting all the shots that were promised. He hunts squirrels and Ian pointed out that one fill of his rifle equals 30 squirrels. That’s more than he ever sees. When the friend realized that he got happy again and Ian says he now loves his rifle.

I already showed you that my Avenge-X prefers to stop at 4100 psi. If I fill to 4350 psi the regulator “burps” after 10 or 15 shots and the point of impact changes. I discovered that while tuning the rifle the first time and it would be foolish not to pay attention to it.


Reader shootski has mentioned several times that he fills his big bore PCPs to lower pressures. He laments the days when Girardoni rifle only used 800 psi to shoot twenty-one .47-caliber lead balls — one of which could kill a man at 100 yards — a fact that has historic proof.

Hunting Guide

Air Arms Shamal

In 2014 I wrote about my Air Arms Shamal precharged pneumatic (PCP) rifle that only filled to 2250 psi. I thought it filled to 2600 psi, but with my carbon fiber tank gauge — 2250 was where I stopped.

Air Arms Shamal.

How this affects you

Instead of focusing on a number such as the fill pressure that may even be incorrect because of errors in the pressure gauge, learn where your airgun wants to be — according to the gauges on your fill equipment and fill it to that level. The object of an airgun is to hit what it shoots at — not to display numbers on a gauge.

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.

43 thoughts on “Quit worrying about fill pressure!”

  1. “Guys, I am in the hospital today, having that kidney stone removed.”

    BB, I’m praying that all goes well for you!!!
    The good Lord knows, we need you! 😉

  2. B.B.,

    First, a prayer will continue to be offered each night (early morning) for a successful procedure, complete and quick recovery.

    Second, although shootski has filled Big Bores to lower fill pressures i have also filled to higher pressures.
    I believe RidgeRunner is the one that mentions the efficiency of the Girardoni airguns (i completely agree with him on this!) more often then i have.
    I have also noticed that PCP storage fill levels have become a discussion topic ONCE MORE on the near perfect 10 year repeating cycle.
    Folks degassing your PCP for storage is a BAD IDEA because it fails to protect the system from moisture and dirt (contaminants) intrusion. Even for long term storage a RATED full charge, in my opinion, is your best choice. Cycling a storage vessel is what work hardens metal and stresses (micro FRACTURES) composites more than filling and storage at full RATED pressure.
    Consult your manufacturers Owner’s Manual for their recommendations to comply with warranty requirements.


      • OhioPlinker,

        You could.

        I couldn’t possibly…i have always carried my Government 1911s in Condition 1; one in the Chamber and 8 in the magazine, action Cocked and Locked.)

        On my airguns it depends on what I’m currently doing and the type of action on the gun.
        But you are correct a pressurized airgun is to be treated as LOADED regardless of the chamber/projectile status.


      • BB

        Glad your procedure went well. I suffer from chronic stone formation myself and, as I think you have too, if memory serves, had a long stay in the hospital due to a life threatening sepsis infection in my kidneys following a laser lithotripsi. My doctor did some tests and discovered that my citrate levels were low and prescribed a potassium citrate supplement that has keep them away for years now. Have you ever talked to your urologist about preventative care?


  3. BB: The words of David in the 23rd Psalm are all precious, but my prayer for you this week is from verse 4. Let those from verse 5 offer you God’s comfort as well. I look forward to a healthy you returning in a few days. Know that you will be in the prayers of your friends and readers, Orv.

      • TOM: Your faith in Him through Christ will make your paths straight. My prayers are for your healing and returned vigor. May we see you here soon, Orv.

      • “Trust in the Lord with all your heart,
        And lean not on your own understanding;
        In all your ways acknowledge Him,
        And He shall direct your paths.” — Proverbs 3:5-6

        Amen! 🙂

  4. FM adds his prayers for your quick, uneventful recovery and complete success of your surgery to those being said by his fellow “airheads.” Be well, amigo!

  5. BB,
    prayers for a good outcome and a quick recovery.

    On the fill pressure, I understand why that happens with unregulated guns like the Condor and my Marauder. I don’t understand the mechanism of why it happens to regulated guns like the Avenger. Any insights as to why it happens?


    • CB,

      The regulator reduces its output in percentages, not set pressures. It does not “know” what the input pressure is. If the input pressure exceeds what it is supposed to for that particular regulator, it does not function properly. Some of the newer high pressure fill air rifles use two regulators, stepping the pressure down to where it is usable and more controllable. I hope I explained this right.

      • RR,
        thanks. I knew that regulators weren’t completely consistent, but I hadn’t thought of the output as a percentage. My only exposure to regulators is on my shop compressed air. If it changes it isn’t much, but I don’t pay enough attention to it to even notice. And of course, that is a completely different range of pressure.

        • CB,

          This one of the reasons I desire to play with the Armada. I want to reduce the fill pressure as low as is possible and still function properly for a magazine of shots.

          That is the reason for the high fill pressures. Folks want a gazillion shots per fill. Not being a target shooter, I personally could care less. When the feral soda cans attack the homestead, I usually break out a sproinger to fight them off, so refilling the reservoir is a moot point.

          • RR,
            that will be an interesting test. I hope you’ll post something here about your results.

            I would like more shots with my Maruader and Puncher. But like you, when it comes to just going out and shooting with my nephews, it’s the Daisy 853s and my one springer that go out the most.


  6. BB,

    As is God’s will, we pray for your safe and speedy recovery.

    As I have stated many times before, I do lament the extreme rise in fill pressures. I have been fiddling with airguns long enough to remember when 3000 PSI was as high as you went or you would likely experience “valve lock”. Those of you who have a Disco or Maximus or the new 3622 that is unregulated, try filling it above 2000 PSI and see what happens.

    What many do not know, remember or even realize is that most sproingers produce only about 1000 PSI. CO2 operates at around 1000 PSI also. A regulated PCP often reduces the output pressure to less than 2000 PSI and typically much lower.

    The valve is what will control the airflow to the pellet. I had a Talon SS that liked being filled to only 1900 PSI. As soon as I can stand the outside temperatures and humidity levels, it is my intention to start playing with my “new” .25 Benji Amada. My goal is to reduce the fill pressure to 2000 PSI or less and still function properly. Once upon a time TCFKAC advertised the Marauder could be tuned to operate at that pressure or even filled with CO2. Have they changed anything?

    Shootski understands where I am going. He has been around long enough and messed with PCPs long enough to have witnessed the climb in fill pressures.

    I have an AV compressor and a carbon fiber tank, both capable of 4500 PSI. I know there are hand pumps that are rated for such pressures. Good luck. I just want to return to the lower pressures of yesteryear. Not only am I old, fat and bald, I am lazy.

  7. While I agree in the big scheme of things, ‘losing’ 200-300psi of pressure/capacity is not nominally a big deal, I do somewhat understand the complaint. Look at this way…If I buy a truck and I pay extra to opt for the extra large fuel tank that holds 36 gallons instead of the standard 20 gallons because I want maximum fuel range per tank, but the truck won’t run right unless I stop the fill at 32 gallons, then I have a legit complaint, don’t I? I am losing 4 gallon capacity or roughly 70 miles of extended fuel range that I paid for.

    If my gun doesn’t work right because I fill to maximum and I have to refill at to a lower setting after 30 shots instead of the 36 I would have gotten on a full fill, does that not constitute a legitimate complaint? I am not really questioning you BB though it may sound like it. I am Just playing devil’s advocate here because I want to learn. I may be wrong about how the whole thing works anyway. Maybe full pressure does not equal full capacity as it would seem to a novice?? I have only been shooting pcps for a couple of years now so still a relative newbie.

    Prayers for you my friend!!


    • Honest Bob,

      Easy to understand why you and many others have felt the manufacturer or builder haven’t held up their end of the deal. Unfortunately there are so many things that effect the results you achieve with your airgun at your location; even from day to day!
      IF you aren’t shooting the very same projectile that the manufacturer used to come up with the numbers then all bets are off. Next issue is that NOT MOST of the manufacturers bother to tune and test the powerplant’s performance. The assembler may, or likely may not, even bother to do a check of the number of turns on the various adjustable controls/features. Almost NEVER will you find a CHRONOGRAPH in the assembly or Inspection/Quality Assurance area.
      I sincerely doubt that even PAir does anything more than check basic functionality in their 10 for 10 (probably not with your choice of projectile) and other post purchase services.
      What is the MV, SD, ES, Shot Count & curve, you are willing to live with?

      Finally, every airgun, even the same model/caliber, from the same manufacturer, and built right after the comparison airgun WILL have some amount of different performance.

      Sorry to bust your (and many other’s bubble) but that is the facts as i find them based on decades of studying
      the Physics of air powered PCP and experience with actual airguns from .177 to .58 caliber to precision Olympic 10M to Custom built .58 caliber Short Rifle.


  8. Tom,

    Praying for a successful surgery and uneventful recovery.

    Seems like the marketeers have found something new to pound on. They have realized that velocity isn’t everything and are now touting the pressures. Hopefully no accidents will occur.


  9. BB

    I, too, would like to offer my prayers for an uneventful surgery and a quick recovery. They may not be as effective since they come from an atheist, but please know that I offer them sincerely.

    I own a Challenger 2009 that I used for competitive 3 position 10 meter. It is non regulated and I filled it to below it’s rated capacity. It would hold its POI for the required 60 shots, but it was my practice to refill it after the first two positions (40 shots plus sighters).

    I had found that when filled to capacity, my sighters were not hitting where they should. It took me some time and effort to figure out what was happening ( I didn’t have a chronometer at the time). At first I thought the rifle needed a half dozen shots to “settle in”, but when I filled to the lower pressure it didn’t. The light bulb finally lit up.

    What part of the firing sequence allows for higher velocity from lower pressure? Is it just the size of the orifices through which the air passes? I have launched potatoes close to a hundred yards with a compressor that only went up to 100 psi, and the valve was a half inch ball valve. I didn’t experiment with it beyond trying to hit pigeons on the neighbors roof. ( that didn’t last long, Mom got a call from said neighbor)

    Nobody was worried about me “putting an eye out”. They were more concerned with the windows and shingles.


    • edlee,

      You wrote this: “What part of the firing sequence allows for higher velocity from lower pressure? Is it just the size of the orifices through which the air passes?”
      A whole bunch of things conspire to do that and the size of the orifices have very little to do with it! Time (known as valve dwell time OPEN) is far more important. Both the reservoir pressure (which drops) every shot without using a regulator, Hammer Spring power/speed, return spring (inside the valve) rate, pellet caused back pressure, current atmospheric conditions and more.
      Simply put:
      Your airgun a Challenger 2009 has a knock open valve.
      The fill pressure is 2,000 PSI. You should able to get at least 70-80 shots without seeing a POI (Point Of Impact) shift at 10 meters even though your MV (Muzzle Velocity may oscillate by as much as 15+ FPS (Feet Per Second) if POI is not stable you can adjust the Hammer Spring preload and Striker length to get the performance you want.
      Tom’s writeup is spot on and should be understood completely if you start changing your powerplants settings.

      B.B. did an extensive test of your air rifle:

      Still have questions? Just ask them i will try to clear things up as you go.


      • Thanks Shootski

        I didn’t buy this rifle until around 2010 or 11. It was so that I could compete in the Veterans wheelchair games. I hadn’t found BBs blog yet and was completely new to PCPs. In fact, my experience with airguns was from my adolescent years with daisy BB guns.

        I read the instructions just as BB did, and made my adjustments based on the consistency of shot placement. I had used firearms for many years and was reasonably proficient with them so much of my routine (sight control, breath control, follow through) was based on that.

        I managed to get the useable string up to 70 and was really pretty happy with that. I, like BB, found that adjusting the trigger weight as low as I wanted ended up with a screw and spring on the ground,, so I did what any ironworker would do,,, and I cut the spring shorter.

        I wish that I had found this blog sooner as it would have saved me an enormous amount of time and effort. But, in the end, even my ham handed efforts were rewarded with a five year run of gold medals. The competition was getting better, too, but I stopped competing due to complications of my spinal cord issues.

        I was lucky enough during those years to have found a gentleman who coached high school and 4H shooting teams at a local shooting club. He was instrumental in my performing as well as I did.

        While I truly appreciate your offer, sadly, that rifle has joined most of the rest of my guns as an occasionally cleaned and oiled closet queen (safe queen, actually). I would dearly love to give them all the attention they deserve, but conditions dictate differently.


  10. Totally stopped worrying about fill pressure … bought another springer!
    Strongly considered a Avenger X Tactical but decided I have enough PCPs. But … if I sell off a Marauder or two?
    A Springfield M1A springer was in the right place at the right time. When I posted the picture of my M1A recently I realized I had not shot it for a long time. Something about heavy springers and reduced recoil makes for enjoyable shooting. Wondered if it was still for sale on P/A and found a refurbished one in .22 for a buck and a quarter. Okay $129.95. What the heck, mine is a .177. Great price and if the refurbishing did not go well, it will be spare parts. Got a refurbished Colt SAA once and it still had a bad seal inside.
    Some were like new.
    Sure enough, I forgot about the safety being reversed but at least if you screw up when using it, it goes into the safe mode. Then again, it was probably in the fire mode while being handled, not so pretty good.
    It also reminded me I still need to get a cheek riser, now two.
    Made the most out of the P/A 4th of July sale and free shipping. Talk about Enablers. Great people.

    Now, back to monitoring the Kitchen Creek Wildfire down the road from me. Latest weekly wildfire in CA.
    You can’t treat fires the same as they do in the jungles of Central and South America here in our southwest.
    Must have left that info out of the “How to sneak into the United States” hand out.

    • Well, well,
      Must be a Fourth of July ‘Fire Sale’ I now have two Wildfires east of me to monitor. The McCain 100-acre fire as well as the Kitchen fire. Not exactly a fine air gun day.

    • Bob M,

      I think i would breed and feed some Cougar Cubs if i lived along the border to help with thinning out the South to North traveling Fire Bugs. I understand they are quite intelligent and can be trained to protect a homestead that they consider to be theirs.


  11. Shootski,
    Great Idea! My daughter said the last fire was actually started by a car. I could comment more but I’ll just let it be.

    I wonder if manufacturers ever consider how deep shooters would dig into their air guns to find the best performance. And do they take their findings into consideration when designing new ones?
    Are we doing R&D for them?

  12. Years ago, at the Roanoke show, I met BB and his friend, Mac. It was there I bought Mac’s Talon SS and determined with my chronometer that it didn’t operate as it should until the pressure dropped down from 3,000 to 2,800 psi. That is one of the rifles I will never sell. For those that don’t yet own a chrony, plenty of choices out there and they cost less than that air rifle you have your eye on. For the most part.

    The Talon has over a half dozen squirrels to it’s credit. Seems the furry rat population has moved on to safer territory and is leaving my bird feeder alone!

    Wishing you a safe operation and speedy recovery, Tom!

    Fred formerly of the Democratik Peeples Republik of NJ now happily in GA

  13. Hope you’re recovering well BB!

    A little off topic, but is there any chance you could do a little accuracy comparison test on the new NateChrony chronograph being sold by Pyramyd Air?

    It looks like an affordable, user friendly and air rifle focused option for those of us who haven’t been able to justify buying one of the more pricey chronographs on the market.

    • jfnz,

      I have a Nate chronograph in hand to test. Please give me some time as it is not a straightforward piece of equipment. I received no manual and I don’t know how to set it up yet.


  14. Everyone,

    I came home yesterday afternoon. This operation was more serious than I imagined, but I had the best doctor (there are only two in the Dallas/Ft. Worth area who can do it) and I’m healing fast. I am still very tired so I plan to take lots of long naps.

    There were two stones — the big one (26.4mm by 21mm) and a smaller one. The doctor told me she got all the pieces. The morning after the operation I was cat-scanned to make sure there were no pieces of stone remaining and I had a sonogram with radioactive dye to make certain the kidney wasn’t bleeding out and the urine was all flowing into the bladder.

    I remained in the hospital an extra day because my bladder had to wake up from the anesthetic. They expect that to happen in 6 hours after the foley catheter is removed, but mine took eleven hours. Until then I couldn’t urinate and they wouldn’t send me home.

    Thanks for all your prayers and well wishes. I will get back in the saddle as soon as possible.

    My thanks to 45Bravo for writing two guest blogs and to Pyramyd Air who watched over the blog while I was gone.

    BB Pelletier

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