Posts Tagged ‘precharged pneumatics’
by Tom Gaylord, a.k.a. B.B. Pelletier
Benjamin Marauder .177 caliber: Part 1
Benjamin Marauder .177 caliber: Part 2
Secrets of loading the Benjamin Marauder magazine
Benjamin Marauder .177 caliber: Part 3
Benjamin Marauder .177 caliber: Part 4
Benjamin Marauder .177 caliber: Part 5
Benjamin Marauder .177 caliber: Part 6
Fixing a Marauder magazine
Benjamin Marauder .177 caliber: Part 7
Benjamin Marauder .25 caliber: Part 1
Benjamin Marauder .25 caliber: Part 2
Benjamin Marauder .25 caliber: Part 3
Wow! More than one month has passed since the last part of this report. I’ve been to the Roanoke airgun show and also out to the rifle range at least 3 times trying to get the data for today’s report, but what a quest it has been! It all boiled down to false confidence in my ability to get the job done. I’m used to certain rifles cooperating with me every step of the way, and this time I got called by the fates who expose pride for what it is.
I’m not going to bore you with all the details, but I will point out the most recent example of my stupidity because it’s a lesson for us all. When I went to the range last week, I thought I was ready to complete my 50-yard test of the .25-caliber Benjamin Marauder. I’d swapped the scope mounts from a previous test because they were too high. The new mounts were lower, and I didn’t have to hold my head as high on the comb. I knew this would help with the accuracy. But then I went to the Roanoke airgun show, and forgot that I’d made this change.
What’s most important about the change, though, are that the new mounts were vintage B-Square adjustable mounts. And the rear ring was jacked up higher than the front. I always liked that setup because it gets the drooper problem taken care of on the first shot — even if there isn’t one! But not if you forget that you did it!
And that’s why this report didn’t happen last week. I had the Marauder at the range with the TX200 Mark III, on which I reported last weekWhen I shot the Marauder, there wasn’t a pellet hole on the paper. And I’m not just talking about the target paper, either. I mean the 2-foot x 4-foot backer paper that I use whenever I have a rifle that’s not known to be sighted-in.
Naturally, I was disappointed. This was a Marauder after all, and I expected it to go right to the point of aim. After shooting just two 8-round magazines, I took the rifle off the line and put it away. I needed to look into the situation deeper and figure out what was wrong.
What was wrong, was that I had forgotten about the new scope mounts. When I looked at the scope back in my office, I immediately saw that the rear was higher than the front. Then I vaguely remembered something about changing the mounts before going to the Roanoke airgun show, so I reread the last report and discovered what had happened. The gun had not been sighted-in with the new mounts. It was obvious that the scope was set up for a rifle with severe barrel droop, and this rifle doesn’t have that.
I even went back to the rifle range last Friday and looked at the backer board where my target and backer paper had been stapled. Sure enough, above where the top of the paper had been there was a hole in the backer board. It had the appearance of a nice rifle group. And some of the holes in the group appeared to be .25 caliber.
Suspecting what happened, I started shooting at an aim point much lower than my anticipated target. Sure enough, my pellet was hitting the paper about 16 inches high and 6 inches to the left. That’s a problem I can deal with! All I had to do was adjust the scope down and to the right, and I was on target. It took me less than 10 minutes to get my groups landing where I wanted at 50 yards. Now, it was time to test the rifle.
The first group was shot with H&N Baracuda pellets. In the past, these were the most accurate .25-caliber pellets on the market, but they have since been replaced by several others, including one huge surprise that emerged in this test! The group measured 1.021 inches between centers. It’s a good group for any rifle at 50 yards, but I did think the Marauder might be capable of better.
I should mention that I was firing two magazines of eight shots each in this test. So the groups that you see have 8 pellets and not 10 in them. I recharged the rifle with air after every 16 shots because the reservoir pressure had dropped to around 2,100 psi by that point. That was as low as I felt it could go and still be accurate.
JSB Exact King
The next pellet I tried was the JSB Exact King, a .25-caliber pellet that’s shown a lot of promise in recent testing. The first group I shot measured 1.447 inches between centers. That’s not very good for a PCP rifle at 50 yards. Interestingly, however, 7 of those 8 shots went onto 0.719 inches, and that is good. I hoped that the one flyer was an anomaly, and that a retest of the same pellet would do better.
The second group of JSP Exact Kings when into 1.094 inches. That’s a lot better, but it still wasn’t what I’d hoped for, so I left the Kings to try other pellets.
Another stunning pellet in .25 caliber is the Benjamin dome. It has no model name, but you could think of it as a Premier pellet because it looks similar to the other pellets in the Premier line. The first group of 8 pellets measured 1.226 inches between centers, which was again larger than I was looking for.
The second group of Benjamin domes measures 1.06 inches. While that’s better, I still thought the rifle could do more.
The last pellet I tried was the .25 caliber Predator Polymag. It showed well in the 25-yard test and earned its place in this test. There really aren’t a lot of options when it comes to accurate .25-caliber pellets, and I think we’ve included all of them in this test. Yes, there are other brands out there, but do they perform? In my experience, they don’t.
The Predator is a hollowpoint pellet that has a red plastic tip in the center of the nose. Normally, hollowpoints fall off in accuracy at around 25 yards, but this pellet doesn’t. That tip seems to do its job.
The first group of Predators measures 1.121 inches between centers. Once again, that’s okay for 50 yards, but it’s nothing to scream about. But the second group measures 0.808 inches between centers. That’s what I was looking for! While the Marauder can’t be expected to shoot that well every time, this group proves that it has the potential. And it does it with a pellet that is acknowledged to be a great hunting pellet!
No .25-caliber airgun has ever been as accurate as the best .22 or .177 guns. What we see from this test is a range of results that represents what the .25-caliber Benjamin Marauder can do at 50 yards. I think these groups show what this gun can do very well. Sure, if you shoot more there will be some smaller groups. But there will also be many more groups that are larger than those shown here. I think we can safely say the Marauder in .25 caliber is capable of putting 8 shots into one inch at 50 yards when you do your part.
The .25-caliber rifle uses a lot of air! I was getting just 16 good shots in this test on a 3,000 psi fill. Compare that to the 32 good shots I got in the test of the .177-caliber rifle filled to the same pressure.
From a handling standpoint, there isn’t a nickel’s worth of difference between the .177- and .25-caliber rifles. The trigger can be adjusted to operate virtually the same, and the stocks feel the same. The one small difference is the .25-caliber gun does move back slightly with each shot. I didn’t feel that with the .177, but I definitely felt it in this test.
If you want a .25-caliber hunting air rifle, I think the Marauder is a good candidate for your short list. It’s powerful, accurate, quiet and reliable. How much more can you ask?
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report comes from a question asked by blog reader Richard, who is perplexed by his Benjamin Marauder air rifle. He said he wondered what pressure he was supposed to fill his gun to, and then at what pressure he was supposed to stop shooting.
As the days passed after asking his question, Richard eventually figured it out on his own and now knows what to do, but today’s report is for all those who haven’t figured it out yet, as well as for those who have held off buying a precharged airgun because they feel there’s so much they don’t understand.
At the Roanoke airgun show last weekend, I talked to a shooter who claimed he pumped and pumped his old Sheridan until it cracked like a .22. Now, I know that’s impossible and I’ll tell you why.
Firearms and airguns are NOT alike!
People think that firearms and pneumatic airguns are alike. The more pressure inside them when they fire, the faster the bullet or pellet goes. That may be true for a firearm (within reason), but never for a pneumatic. You see, a pneumatic airgun has something that a firearm doesn’t have — a valve.
The pressure generated by exploding gunpowder gets directly behind the bullet and pushes it. More pressure equals higher velocity — within reason. There’s nothing in the way of the expanding gas to prevent it from pushing on the bullet.
In a pneumatic gun, however, there’s a valve. That valve has to open before any of the pressurized air can get behind the pellet. If the air pressure is too high for the valve to open, it doesn’t matter how much pressure there is — the pellet is going nowhere. That’s the difference between a firearm and a pneumatic airgun. So, pumping or pressurizing a pneumatic rifle beyond its design limit doesn’t increase the velocity — it slows it down and eventually stops it altogether.
Therefore, Richard was asking how he was supposed to know the max fill pressure of his gun so it would operate correctly. He wondered that because of conflicting information from Crosman, my blog and probably from other sources on the internet. The fact that the Marauder lets you adjust the maximum fill pressure just made this more confusing for him, and I can see why.
He asked me how he was supposed to figure out the max fill pressure and at what pressure he should stop shooting — the starting and ending fill pressures. There are several ways to find this out. The easiest way is to use a chronograph. To do this, you fill to a given pressure — say 3,000 psi — and start shooting through the chronograph. If the velocity of the pellets continues to rise as shots are fired, the valve isn’t opening all the way; and you know that 3,000 psi is too high for a starting fill pressure.
As you continue to shoot, the velocity will stabilize at some point. When it does, you know that the valve is now opening all the way on each shot. Of course, you will have shot several shots past this point before you recognize it, but usually it will be a very little pressure above what remains in the gun when you notice it. So, fill the reservoir again and watch the needle on your fill gauge. When it stops rising fast (if you’re using a scuba tank) and starts rising more slowly, you’ve opened the inlet valve of the gun’s reservoir and are now adding air to the reservoir. Add just a few hundred pounds of air by watching the gauge on your tank, then shut off the valve and note the pressure at which you stopped. Maybe it will be 2,600 psi. If the gun fires as fast as it did before, you know that the max fill pressure for your gun is at least 2,600 psi or maybe a bit more. Refine this by iterating the process.
The following graphic shows the relationship between pressure and velocity as I have described it here.
What if you don’t own a chronograph? This may be Richard’s dilemma. Is there any way he can figure out the max fill pressure and where to stop shooting?
Of course there is. Airgunners a hundred years ago didn’t have chronographs, yet they did fine by watching what their guns would do. If they wanted to know how powerful their guns were, they shot them at an anvil and looked at the lead splat. If they wanted to know when to stop shooting, they watched the guns and when stopped when they could see the bullets coming out of the barrel. They filled their guns until they couldn’t pump anymore, so max fill pressure was taken care of.
But Richard shoots a gun that’s much faster than a 100-year-old pneumatic. His pellets don’t make splats — they disintegrate! And he fills his rifle to a much higher pressure from either a scuba tank that gives him very little feedback or a triple-stage hand pump that doesn’t have much more feedback.
How does he know when to stop filling and when to refill the gun? Simple, he watches his target and sees where his pellets land.
Let’s take an example and have Richard fill to 3,000 psi, then shoot at a bullseye 35 yards away. If the pellets are climbing while he aims at the same aim point every time — making a vertical group, Richard knows the velocity isn’t stable. He doesn’t know what the numbers are — just that they aren’t stable.
Then, when the rifle starts grouping all the shots together, he knows the velocity has stabilized. Like before, by the time he notices this, he will have shot past the optimum starting fill pressure; but he can always fill to a few hundred psi more than the gun has in it at the point he notices, and eventually he’ll find the optimum fill pressure. The graphic below illustrates this.
Finding the stopping pressure is just the reverse of this. Shoot until the pellets start wandering on the target, again (usually dropping down, again, but sometimes just wandering to one side or the other). Then, you can start filling the gun, and the ending pressure will be a few hundred psi above where the gun begins to accept pressure. From now on, you’ll know approximately how many shots or magazines you can get from a fill; or, if there’s a gauge on your airgun, you’ll know when it’s dropped off the power curve.
You don’t know until you know. You know?
You can read about this all day long and never understand it. This is something you must experience firsthand — as in shoot a PCP and watch it happen. The first time you see it, you’ll understand…and forevermore you’ll wonder why others have so much trouble understanding how precharged airguns work.
by Tom Gaylord, a.k.a. B.B. Pelletier
Benjamin Marauder .177 caliber: Part 1
Secrets of loading the Benjamin Marauder magazine
Fixing a Marauder magazine
Benjamin Marauder .25 caliber: Part 1
Benjamin Marauder .25 caliber: Part 2
I told you this report was going to be a different kind of test, and today I’ll prove it. I shot the .25-caliber Benjamin Marauder off a rest at 25 yards, but the purpose was not to learn if the rifle is accurate — I already knew it is. And 25 yards is hardly long enough to show the accuracy potential of this powerful PCP.
No, I told you that I would be searching for the most accurate pellets in this rifle. You see, unlike .177- and .22-caliber guns, the big .25 doesn’t have that many accurate pellets. Going into this test, I only knew of 3 — the H&N Baracuda (also branded as the Beeman Kodiak), the Benjamin dome and the JSB Exact King. Other .25-caliber pellets I’ve tested were not accurate enough to be considered. Today’s test is to establish that the 3 good pellets are still good in this test rifle and to see if there’s another good pellet or 2 out there.
The rifle is now scoped with the UTG 6-24X56 AO scope with illuminated reticle, which I’m also testing for you. I won’t get into that evaluation in this report, but I will use this test to report on that scope. This scope has high rings that come packaged with it.
Testing pellets rapidly
Time is a commodity in short supply around here. It takes a long time to test something, then pictures have to be taken and it takes even more time to write it up. Normally, I shoot 10-shot groups for accuracy, but I told you I was going to do things differently today, and this is where it starts. Instead of shooting 10-shot groups (or 8-shot groups because the .25 Marauder circular magazine only holds 8 pellets), I decided to shoot 4-shot groups. The results of those groups would tell me which pellets were worth testing more closely. But testing more closely won’t be at 25 yards. It will be out at 50 yards.
Since I’d just mounted the scope, I had to sight-in the rifle, and for that I loaded a full magazine with 8 H&N Baracudas. Sight-in took just 2 shots, so the first group for the record was 6 shots instead of 4. As predicted, it was a tight 0.376 inches at 25 yards. Of course, some of that is due to the lesser number of shots, so bear that in mind. Also, bear in mind that a group of .25-caliber pellets will look much larger than the same size group of .177-caliber pellets.
JSB Exact King and Benjamin dome
Next, I shot 4 each of the JSB Exact Kings and Benjamin domes. Both performed exactly as expected. The 4 Benjamin domes went into 0.196 inches. Of course, I would expect this group size to double with 10 pellets, but it’s still the kind of accuracy I was looking for.
I shot the first 3 JSB Exact Kings into a very tight 0.11-inch group, but the fourth shot was a called pull to the left. It opened the group to 0.383 inches; but since I know that I pulled the shot, it doesn’t phase me. This pellet also made the cut for more testing.
Three JSB Exact Kings went into 0.11 inches at 25 yards. That’s the larger hole on the right. A pulled fourth shot that was called opened the group to 0.383 inches, but that doesn’t bother me. This one is a keeper, as well.
The only other pellet that showed promise in this test was the Predator Polymag. Four of them went into 0.274 inches at 25 yards. That’s good enough to earn a chance to shoot at 50 yards in my book.
The other pellets
As I said before, the .25-caliber pellet is not as uniformly accurate as the .177 and .22. Until this test, only the first 3 pellets I shot had shown any promise. Now, we have a fourth. To show you what some other pellets look like in comparison, here are 3 more that didn’t make the cut.
The results of 4 RWS Superdome pellets tell the story of the .25 caliber very well. Four went into a group that measured 1.378 inches between centers. You can clearly see there’s no need to shoot 10 pellets, when just 4 make a showing like this.
Next, I tried the pellet that was the best .25-caliber pellet for many years in the 1990s. Until the H&N Baracuda came out in .25 caliber, the 20-grain Diana Magnum was the pellet people chose for accuracy. Certain individual guns may have done better with other pellets, but the Diana Magnum was considered the best all-around .25-caliber pellet of its day.
Not surprisingly, Diana Magnums turned in the smallest group of the three pellets that were not selected to go on to longer-range testing. Four went into 0.588 inches at 25 yards.
Beeman Ram Jet
Another pellet that has left the stage is the .25-caliber Beeman Ram Jet. It was supposed to be a domed pellet that also performed like a wadcutter, but accuracy was never this pellet’s strong suit. Four of them made a 0.769-inch group at 25 yards.
I hope from these results that it’s clear why I went with 4-shot groups instead of 10-shot groups. I never planned on testing the .25-caliber Marauder at 25 yards, except to prepare for the 50-yard test, which will be next. I think you can see the clear differences between the pellets that were selected and those that missed the cut. More than any other caliber, the big .25 is an all-or-nothing caliber. And there aren’t that many pellets to choose from.
One more thing I want to report today is how the trigger now performs. I adjusted it before this test and got it exactly where I want it. I won’t say that it’s better than the trigger on my .177 Marauder, but it’s just as good. The Marauder trigger is something Crosman can be proud of, for it surpasses most PCP adjustable triggers I’ve tested. This one now has a positive stop at stage 2, followed by a very light, crisp break. It allowed me to hold very precisely and know when I pulled my shots, which only happened once during this session. This trigger will certainly do!
Next, I plan to shoot the rifle at 50 yards with these 4 pellets. That should give us a good idea of the long-range capability of the rifle. If the results suggest it’s capable, I may attempt a 100-yard test, as well. I need for the shooting conditions to be perfect to do it; but if they are, we may see the real potential of the big Marauder.
by Tom Gaylord, a.k.a. B.B. Pelletier
It’s taken me awhile to get back to this pistol because I injured my hand, so I couldn’t fill the Hatsan AT P1 PCP air pistol from the hand pump for a couple of weeks, but last Friday I was at it again — probably for the last time. You may remember that I discovered that the AT P1 likes a fill pressure of 3,200 psi — which is sort of ironic in light of several recent reports I’ve done. This time, I used the Hill pump to fill the gun to that pressure to see if there are 10 good shots on a fill. That was the problem before — the circular clip holds 10 pellets, but the gun didn’t seem to want to shoot more than 7 of them on a single fill of air.
I decided that instead of wasting time with a lot of different pellets, I would concentrate on the one good pellet that I knew gave the best accuracy. That’s the Beeman Kodiak. First, I filled the gun to 3,200 psi, then loaded the clip and inserted it into the gun. Someone asked me how I held the gun to shoot it, given that it’s scoped with a Leapers UTG 3-9X40 AO rifle scope. The eyepiece has to be held within 2-3 inches of the eye in order to see the image. There’s a way to hold the gun that uses the scope as one of the handles, and that’s what I did. I photographed it for you, so you can see it as I describe the hold.
I hold the back of the scope at the eyepiece and let my hand separate the rear of the scope from my sighting eye by the required distance. My hand is pressed against my safety glasses to maintain the separation. The weight of the pistol rests directly on the bag, so all my other hand does is keep the pistol steady. With this hold, I can squeeze the trigger without moving the gun.
This hold is one I learned while shooting the LD Mark I pistol from Tim McMurray. That’s a Crosman Mark I Target pistol that Tim converts to add a longer bafrrel, a CO2 tank hanging down from the grip and a rifle scope mounted on top — just like this one. With the LD, I rested the external tank on my chest and held the scope like you see here. That gave me near-rifle accuracy.
The result is a steady hold — especially when you consider I’m shooting only 25 yards. I don’t recommend holding a recoiling firearm pistol this way, but you can get away with it on a PCP.
All targets were shot at 25 yards. The first target looked very good until the final shot. I could see that the pistol was grouping low and to the left, but all I was interested in was the size of the group. It could always be moved later with a simple scope adjustment. The group that formed looked very encouraging until the last shot, as I said. I could clearly see that one go high and into the center of the bull, ironically enough. But when I walked downrange to examine the target more closely, it wasn’t as good as it had seemed. A line of four shots appears to the right of the main group, and they’re strung vertically up to the center of the bull. The last one is the highest one. I never saw the other 3 shots in the string, so they could have been any of the preceding 9 shots. All I could see through the scope was the large group that formed at 7 o’clock on the edge of the bull.
I guess this first target took the wind from my sails. It was no better than any of the previous targets shot with this pistol. My idea that a higher fill pressure would keep 10 shots in a tighter group was bogus. But I still had time on the range, so I thought something else was in order. I adjusted the scope higher and to the right just a little, to correct for where the Beeman Kodiaks had grouped. Then, I loaded the gun with 10 JSB Exact Monster pellets. The Monster pellet weighs 25.4 grains, making it even heavier than the .22-caliber Beeman Kodiak. And it’s a JSB. I wondered if this might be the pellet that turns things around for the AT-P1 pistol.
Alas, it wasn’t. It turned things around, all right, but not for the better. The pellets were all over the place! In the end, 10 of them printed a group measuring 1.933 inches at 25 yards. It’s more of a full-choke shotgun pattern than a group shot from a rifled barrel!
Now, I was really downhearted. I switched back to the Kodiaks and give them one final try. The gun was, again, filled to 3,200 psi, and 10 more pellets went downrange. This time, the results were not as good as the first time. Ten pellets made a group that measured 1.211 inches between centers. It was higher on the target and also centered better, which proves my earlier statement that the group can always be moved by adjusting the scope, but things were not getting better.
Outcome and final evaluation
I put a lot of time and energy into testing the Hatsan AT-P1 pistol. The reward was not worth the effort, in my opinion. While I agree that Hatsan does know how to make a fine precharged air rifle, the AT-P1 pistol is not as refined as the rifles they make. It’s too large and too coarse for what it delivers. I wanted it to succeed because there aren’t that many nice PCP pistols to choose from, but the test results do not live up to the hope.
I think that if you’re interested in an airgun like thi,s you should look at the AT-P2 pistol, which comes with a shoulder stock. That way, you won’t have to learn how to hold the gun like I did here. As long as you know how few shots you’re going to get on a fill of air (7) — and you manage that, you’ll be fine.
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report came from a question asked by blog reader GunFun1:
“How do airgun manufacturers come up with the maximum fill pressure for their precharged airguns?”
He went on to say:
“I guess it is safety related and to protect the o-rings also. And if the gun isn’t adjustable for the striker and spring I guess they test to see if the gun will get valve lock or something? Or is for the fact that most hand pumps won’t go too much above the 3000 psi fill level with the exception of a few brands?”
What I am about to tell you has been collected from dozens of meetings and tours through airgun companies. I’ve been in the engineering departments, talked to the development engineers, and seen the CAD systems and the prototypes they work on. I’ve also had long discussions with smaller airgun builders like Dennis Quackenbush and Gary Barnes. I know how they approach this problem. So, I can tell you what I’ve seen. That’s not the same as a full disclosure report, but I don’t think you’re going to get that anywhere.
Doing what works is Job One
Airgun companies don’t “come up with” the maximum fill pressure at all. At least they don’t do it as an initial calculated engineering step. It’s not a primary goal, except in a few instances I’ll mention. Instead, what they try to do is design and then build a precharged airgun that works. One that shoots pellets out the muzzle. That’s always the first objective.
In coming up with “what works,” each company has something definite in mind. One company may want to build a 10-meter target rifle that fires an 8-grain .177 pellet at 575 f.p.s. for at least 120 shots from a fill, and they don’t want the velocity to vary by as much as 10 feet per second throughout the entire shot string. There are several paths available to them — things like pressure regulators, balanced valves and so on.
Another company wants their gun to propel a 30-grain .22-caliber pellet at 1,000 f.p.s. They are making a hunting rifle, and their first goal is to get the power they are seeking. After they get it, they’ll then look into getting the most number of shots from a single fill.
A third company wants to build a rifle that gets a lot of shots in the 25 foot-pound region. Their primary goal is the number of shots they can get at around 25 foot-pounds.
Where does fill pressure fit in?
In all of this, the fill pressure hasn’t been mentioned, but it has been in the backs of all the minds working on the primary goals. For example, most airgun manufacturers know that shooters in the United States have easy access to air at pressures up to 3,000 psi. So, a gun that has a 3,000 psi fill limit is going to be received better than one that needs to be filled to the 4,350 psi that some German guns require. The United States is not a very big airgun market in general; but for guns that develop great power, it’s probably the biggest market there is. Anyone who builds an airgun of great power would be foolish to also build it to accept a 300 bar/4,350 psi fill. Doing so would cut out their biggest potential market.
On the other hand, the United States is a relatively small market for high-end 10-meter target guns — guns costing between $1,700 and $3,200. So making a gun in that category that also accepts a 300-bar fill isn’t foolish at all. If the European market for these guns is that much larger than the U.S. market and if it’s that much easier to get the higher pressure air in Europe, it makes perfect sense to build guns like that (for reasons I will discuss in a moment).
However, making a low-cost, youth-oriented target rifle that needs a 300-bar fill would be suicide! That’s because the world market for rifles in that category is located in the U.S. We have almost a million kids each year competing in 10-meter target matches, and that’s a number that’s been verified by the NRA. That’s why Daisy, Crosman and AirForce Airguns all have models in that category, and they know that to boost the fill pressure of their guns to 300 bar would be the kiss of death.
What about the boutique makers like Quackenbush and Barnes? They know their markets well and tend to build guns that fill to 3,000 psi or less. It’s true, many of the Quackenbush Outlaw Long Actions will accept higher fill pressures and still work well, but that’s an anomaly. They’re designed to use a fill pressure of 3,000 psi.
And what about the Korean precharged guns? Many of them will also accept a higher fill pressure and still function. In their case, like the Quackenbush guns, I think the design goal was 3,000 psi, but a too-heathy valve return spring boosted the top threshold beyond the goal. With guns like these, a shooter is rewarded for chronographing his shots and establishing what the actual fill pressure of his specific gun is before heading out to the field to hunt. He can get by with a 3,000 psi fill, but time spent on the chronograph will reward him with extra velocity for the shots he gets on each fill. What it usually won’t do is add more shots to the total per fill.
Can fill pressure be a primary goal?
While it normally isn’t a primary design goal, it is possible to make the fill pressure limit one of the primary goals for the airgun’s design. Tim McMurray and Larry Durham were the first ones to succeed in doing this in a very big way when they designed the USFT rifle. With a fill pressure limit of around 1,600 psi (these rifles all vary just a little on the exact pressure limit), they get 55 good shots of .177 Beeman Kodiaks traveling over 900 f.p.s. How is that possible? Well, there are 3 things that make it possible. One is a 25-inch barrel that gives a longer time for the pellet to accelerate, and another is a huge air reservoir that stores a lot of air at the recommended fill pressure. The third essential thing is a valve and hammer that are balanced perfectly to open the valve and hold it open long enough for the pressurized air to flow into the barrel and get behind the pellet.
Even before the USFT came about, Gary Barnes made one airgun that got a notable velocity on extremely low air pressure. With his outside lock airgun, Gary was able to get .25-caliber pellets over 25 foot-pounds of energy (a 20-grain pellet going 753 f.p.s.) on just 600 psi. That sounds incredible until you recognize that airguns were doing that and much more in the 1600s and 1700s. They had to because that was about as much air pressure as they could get into the gun!
Barnes’ outside lock gun did not shoot at a steady velocity. The first shot was the most powerful, and each shot thereafter dropped in velocity somewhat. But it was still possible to get 9 shots from his gun — all from an initial charge of 600 psi. His rifle has a 32.75-inch barrel, which is needed to extract every last bit of energy from the low air pressure. And the secret of his valve is that it’s held open not by impact but by a pair of cams that come into contact and are locked to travel together through an arc as the hammer falls. The length of the arc determines how long the valve remains open. So, the velocity of this gun can be regulated by the hammer spring, the valve return spring, and by the size and shape of both cam elements. It’s an ingenious design that dates back to the very early 1700s.
Knowing that low-pressure operation was possible for a PCP, I went to Crosman in 2006 with a proposal to design a low-cost, easy-to-fill PCP single-shot rifle. I’d been told by another airgun designer that my idea was impossible the year before, but I knew from the USFT and the Barnes gun that it was very possible. The result of that project was the Benjamin Discovery.
Why fill to higher pressure?
The next question we must ask is, if it is possible to get many good shots on lower fill pressure, and the Benjamin Discovery proves that it is, then why would anyone ever build a gun that takes a fill pressure that’s extremely high? Why, for instance, would a gun need to be filled to 4,350 psi? One good answer is the gun has a pressure regulator that drops the reservoir pressure to a lower pressure that the firing valve can handle. If you can drop 4,350 psi to 1,800 psi for a valve, you’ll get many more shots from the gun than if the valve had to operate throughout a range of pressures. That’s because no matter how a mechanical valve is designed, there will always be an upper limit at which it will work and a lower limit, below which it will stop working.
While such a system SOUNDS like the perfect design, you need to consider that the pressure regulator takes up space inside the reservoir that cannot be filled with air; and the valve also needs a small chamber of air at the lower pressure where it’s been designed to operate. That chamber also takes up some space where pressurized air cannot be stored. So, there’s a tradeoff when installing a regulator. You need enough room inside the reservoir to make the regulator system worth the loss of reservoir volume.
A more sophisticated system
A better way to use air at a higher pressure is to employ a computer-operated solenoid to open and close the firing valve. Then, you don’t need either the regulator or the air chamber. The electronic valve does all the work. If you also put a pressure sensor inside the reservoir that can tell the computer how much pressure it has to work with, the computer can calculate exactly how long the electronic valve has to remain open, giving you shot after shot at the same velocity, even when the air pressure drops by 2,000 psi. This is how the Benjamin Rogue works.
While the .357-caliber Rogue hasn’t been a huge success in the marketplace, the proprietary way its valve operates gives Crosman an edge in the PCP market. If they were to put their valve on a smallbore rifle built for general hunters and shooters, and if they could keep the price under control, they might just have the next generation of sporting PCPs. I don’t mean the gun has to be cheap, either. With Air Arms sporters selling for $1,000, and both FX and Daystates pushing $2,000, there’s plenty of room for a premium-priced Benjamin sporter with the Rogue-type electronic valve. It can’t look like it was sired by a boom box and a black rifle, and it has to be quiet, have a deadly accurate barrel and a trigger to die for; but such barrels are available, and Crosman knows how to make good triggers and quiet guns.
So, GunFun1, this is my answer. Fill pressure isn’t normally the first thing on the minds of airgun designers. Many of them just build guns that work, and the fill pressure falls in place toward the end of the project. Those who are more savvy know what the market will allow, and those who are really sharp know what the market is looking for.
by Tom Gaylord, a.k.a. B.B. Pelletier
Today, I’ll test the .25-caliber Benjamin Marauder for velocity and also get the shot count. From past tests done by my friend Mac, we know this rifle should be in the 38-40 foot-pound region, but today is the day the rifle gets documented by me. No tuning has been done to this rifle to the best of my knowledge; so, although it’s 3 years old, it’s also straight from the box.
The rifle was filled to 3,000 psi and the first pellet tried was the .25 caliber H&N Baracuda. This domed pellet weighs 31 grains; and in the test rifle, it averages 778 f.p.s. That’s good for an average 41.68 foot pounds of energy at the muzzle. The total velocity variation in an 8-shot string was 774 to 782 f.p.s. That’s just 8 f.p.s.
The next pellet I tested was the 27.8-grain Benjamin dome. This pellet averaged 805 f.p.s. with a low of 802 and a high of 808 f.p.s. That’s just 6 f.p.s. for the total spread. The average muzzle energy for this pellet was 40.01 foot-pounds. The Benjamin dome has been one of the most accurate .25-caliber pellets around since it first came out, so it’ll be interesting to see what it can do in the test rifle. I always think of this pellet as the .25-caliber Crosman Premier, though the company doesn’t brand it that way.
JSB Exact King
Next, I tested the 25.4-grain JSB Exact King. This is another fine domed pellet that has been one of the most accurate .25-caliber pellets since it was introduced a few years ago. It’s also light enough to travel faster than most of them.
These pellets averaged 831 f.p.s. in the test rifle, for an average muzzle energy of 38.96 foot-pounds. The spread went from a low of 829 to a high of 835 f.p.s. That’s another one that’s just 6 f.p.s.!
The last pellet I tested was the 26-grain Predator Polymag — a high-tech hollowpoint pellet that has a cone-shaped plastic nose for improved aerodynamics. This pellet averaged 814 f.p.s. in the test rifle and delivered an average 38.26 foot-pounds of energy at the muzzle. We’ll see how accurate it is in the next test. I have no experience with the Predator in .25 caliber. The spread went from 808 f.0.s. to 820 f.p.s., for a total of 12 f.p.s.
I got just two 8-shot magazines from a charge before the velocity started dropping. By dropping, I mean the velocity was falling straight off with each shot. I could stretch the total to 3 mags, which is 24 shots, if I wasn’t trying to shoot groups at 50 yards. The velocity spread would triple with the final 8 shots, which would take 6 f.p.s to 18 f.p.s. and 12 f.p.s. to 36 f.p.s. As long as you keep your range to 35 yards or less, those final 8 shots should work fine.
Here’s the part of the report many of you have been waiting to read. The test .25-caliber rifle is noticeably louder than the .177 Marauder, but it’s still not loud. I tested them side by side. The .177 Marauder is just so quiet that everything else sounds louder in comparison. And now that I’ve dialed back its velocity to 965 f.p.s., it’s probably quieter than it was when it was pushing out pellets at over 1,000 f.p.s. The .25 has more of a crack to its discharge, but the sound it makes is still quieter than all magnum spring rifles I’ve tested. So, it’s quiet too — just not as quiet as the .177.
I said I wasn’t going to mention the trigger again; but when I compared the trigger on the .177 Marauder to the one on the .25, the difference was noticeable. The .25 has a first stage that’s too short and a stage 2 that’s too long. There’s some creep in the second stage, so I do need to address that. I may not mention it again, but I’m doing so now to let you know there’s a difference between a factory trigger, which the .25 has, and one that has been adjusted.
My personal feelings
I don’t often mention how I feel about airguns, but I think I have to here. I do not care for .25-caliber airguns. I’ve found them inaccurate; wasteful of air; requiring expensive pellets; and, in general, I find they’re not able to keep up with a good .22. The TalonP pistol was an exception to that except for the cost of the pellets, but it was the exception that proved the rule.
I’m rooting for this .25 Marauder, though, because I know many readers prefer .25 caliber for hunting. I have to note that during chronograph testing the pellet trap was rocking the table it sits on because the impact of the pellets was so great. So, if this Marauder turns out to be a tack-driver, it may change my opinion of the quarter-inch bore just a little.
by Tom Gaylord, a.k.a. B.B. Pelletier
This report is an emotional one for me. The last time I tried to report on the .25-caliber Benjamin Marauder, I became very ill and it took me two years to complete the test. In fact, I never did complete the test myself because I was in the hospital part of the time. My buddy, Mac, drove from his home in Maryland to Texas to test airguns for me so he could bank a lot of data and pictures that allowed me to write my blogs from a hospital bed. Mac is now gone, and I’m starting all over again with this rifle.
I’m revisiting the .25-caliber Marauder because I never really got to test it properly the first time. Also because having tested the .177 Marauder, I felt this big gun needed to be reported at the same time. You see, Marauders are good sellers at Pyramyd Air, and several blog readers asked for this specific report.
There’s one more reason for testing this particular Marauder. It’s an entirely different rifle than the .177 we’ve been testing. Yes, all the controls work the same on both rifles and the external dimensions are the same, but a .25-caliber pellet changes the very nature of the rifle in the same way that a one-ton pickup truck differs from a compact truck from the same manufacturer. The .25 Marauder is a BIG air rifle! Big in terms of the magazine and the hole at the end of the barrel. So, this isn’t the quiet little sniper rifle we’ve come to know. This is a hunting air rifle.
I linked to the recent tests of the .177 Marauder simply because I won’t be covering all of the same ground here that I already covered there. This report will cover new ground.
The lauan stock
We are fortunate to have a test rifle with the much-maligned lauan wood stock. It may be made from lauan…I don’t know, but I’ve read so many bad remarks about this stock that I was shocked to realize that this test rifle has one. Shocked because it isn’t bad at all! It has a nice plain grain. It feels lighter than the beech stock on the earlier .177-caliber Marauder we’ve been looking at, and it’s shaped just as nicely. The checkered areas have grown smaller on the new stock, but the cheekpiece still rolls to both sides of the butt, making this an almost fully ambidextrous rifle. Only the location of the bolt handle, which cannot be changed, favors right-handers over southpaws.
By the way, another name for lauan wood is Philippine mahogany. I’ve seen this wood used in furniture, and it doesn’t receive such a bad rap. It’s a hardwood, but it grows fast enough to be a renewable source of wood for many markets, including plywood products. I think the bad reputation comes from the fact that lauan is often used to skin low-quality hollow-core interior doors. People see that these doors can’t stand up to outside environments, and they think it’s because of the wood used in them. But lauan is not especially weak when used by itself.
I do find this wood to be thirstier than beech when I rubbed the stock down with Ballistol. So far, it’s soaking into the pores quite fast, leaving a dry, matte surface behind.
The test rifle has no scope mounted, so I’m taking the opportunity to install a new UTG 6-24X56 AO Accushot SWAT scope that Leapers sent for me to test. I’ll give you a separate report on the scope, so I’ll just mention it for now. The scope comes with 30mm rings that have Weaver bases, and the Marauder scope rail is for 11mm bases; fortunately, I also have a set of UTG Weaver-to-11mm or 3/8″ dovetail adapters that allow Weaver rings to fit on 11mm rails, so these rings will fit.
Power and setup
I can tell you right now that this Marauder rifle is shooting in the 38-40 foot-pound region, so it’s a proper thumper! I know that from the last set of tests Mac ran in 2010. But I plan to run the tests all over, just as if I never tested the gun at all. I probably won’t tune the rifle to shoot with less power or at a lower maximum fill pressure because we’ve already seen how that goes in the test of the .177 Marauder. I do plan to adjust the trigger to be as nice as the one on the .177 rifle, but I doubt I’ll say much about that because it’s ground we’ve already covered.
The rifle is set up to work with slightly less than 3,000 psi right now, and I don’t see changing that. I’ll confirm what the max pressure is, and only if it’s several hundred pounds below 3,000 will I make any adjustments.
The accuracy test is where I plan on spending most of my time. There are so few accurate .25-caliber pellets, so I’ll do some comparison testing with several pellets at 25 yards. The best pellets from that test will make it to the 50-yard test. I’ll modify my 25-yard test to include more pellets than I normally shoot because the world of .25-caliber pellets is so small that we really can’t afford to overlook a possible good one.
.22 caliber Marauder
While I test the .25-caliber rifle, I’m awaiting the arrival of the new Marauder with synthetic stock. I hope to get one of those in .22 caliber, which will give me my first chance to test this rifle in that caliber, as well as testing the new configuration stock and the altered trigger.
The rifle I’m now testing is 3 years old and was made in .25 caliber from the beginning. The magazine is therefore much thicker than one made for a .22-caliber or .177-caliber rifle. Instead of holding 10 pellets like the 2 smaller calibers, the .25 caliber magazine holds 8.
The rifle’s remaining dimensions and specifications are the same as those of the smaller-caliber Marauders. The overall weight will vary with the density of the wood in the stock, but this new wood seems to be less dense than what was used in the past.
When I picked up the test rifle, I noticed that it’s still holding a charge of air. The last time it was shot was in April 2012, so how’s that for holding a charge?
So, sit back and relax. There’s a lot more Marauder coming your way!