by Tom Gaylord
Writing as B.B. Pelletier

Benjamin Marauder air rifle Gen 2
Second-generation Benjamin Marauder in a synthetic stock.

Part 1
Part 2
Part 3
Part 4

This report covers:

  • Not the normal test
  • Trigger adjusted again
  • The goal
  • Velocity test — JSB Exact Kings
  • Early hiccup!
  • Striker adjustment 1
  • Striker adjustment 2
  • Change of plans
  • The rifle’s performance with this adjustment

This is a continuation of the test I’m running on the .25-caliber gen 2 Benjamin Marauder. So far I have evaluated the rifle as it came from the box, adjusted the trigger, installed the exciting new UTG 2-16X44AO Accushot scope and UTG rubber armored folding metal bipod, sighted the rifle in at 25 yards and installed the RAI modular stock and folding butt extension. Then I went to the 50-yard range — twice — and shot the rifle for accuracy. That was where I discovered that the .25-caliber JSB Exact Kings are the best pellets for this rifle. And the .25-caliber Benjamin domes that have no brand name are a close second.

Not the normal test

Veteran readers will see this is not the kind of test I usually run. Normally I describe the characteristics of a gun in Part 1, test the velocity with several pellets (and power settings when appropriate) and things like the cocking effort and trigger-pull in Part 2 and finish with an accuracy test in Part 3. I do it the same each time so readers will always know what to expect from one of my tests. But this Marauder is different. This is my personal airgun that Edie and I bought for extended testing and modification. I am testing it the way I would test something for myself.

I had already tested a .25-caliber first generation Marauder back in 2013. That test alerted me to the performance characteristics I could expect from this rifle, so many of the mysteries were already solved. Despite what you may think, there isn’t that much difference between the rifle I’m testing here and a first generation Marauder in the same caliber. The trigger was modified so it could be moved back in the frame, but the performance remains about the same.

Trigger adjusted again

I mentioned in Part 4 that I didn’t like the way the trigger was adjusted. Stage one was too long — probably because the hand grip of the RAI conversion places my trigger finger much closer to the trigger blade. This is the reason I don’t like an AR15 configuration that much. But I have fixed the trigger on my AR15 by installing a Guiseley competition trigger and adjusting it to suit my preferences. So, after the last test with this Marauder, I adjusted its trigger again. I adjusted stage one to be much shorter, which shortens the entire trigger pull. Then I adjusted stage two to release as light as I felt was safe for a sporting rifle trigger. It’s still above 2 lbs. at the release. There is still some movement in stage two, but it’s not the jerky feeling of trigger creep. It does make the rifle easier to shoot with precision.

The goal

There are two objectives to today’s test. First I want to see the velocities of the first 16 shots following a 3000 psi fill the way the rifle is currently set up. Only one pellet interests me — The JSB Exact King. I noted in both trips to the range that the first 8 shots were always more accurate than the second 8 shots. I want to see what those velocities are, and if they vary by a lot, which I strongly suspect.

The second goal is to adjust theΒ  striker spring tension to achieve a tighter velocity spread. I have been given lots of “advice” on modifications I can do to improve the power of this airgun, but that’s not what I want. Although I don’t know the numbers yet, I think it’s powerful enough for me as it is. I’m looking for 16 accurate and consistent shots. If I want sheer power I have a .25-caliber AirForce Escape that generates nearly 100 foot-pounds; I don’t need this Marauder to compete with that. The Benjamin domed pellets, which are only slightly less accurate than the JSB Kings, should follow along with any changes I make.

Velocity test — JSB Exact Kings

I filled the rifle to 3000 psi and loaded 8 JSB Kings into the magazine. The first shot was 850 f.p.s. on the nose, which means the rifle generates 40.47 foot-pounds at the muzzle with this pellet. While that is good, I can accept less power for more shots on a fill and greater stability. Here is the first shot string.

First string after a fill
Shot……..Velocity (f.p.s.)
1……………..850
2……………..850
3……………..853
4……………..847
5……………..843
6……………..845
7……………..841
8……………..839

The average for this first string is 846 f.p.s., which equates to a muzzle energy of 40.36 foot-pounds. The total spread is 14 f.p.s.

But the string tells me a lot more. The rifle is maxed out at the current setting. See how it rises only a small amount on shot 3, then goes into a steady decline? I know the next string will be both a steady velocity decline and probably a much greater spread from the first shot to the last. Let’s have a look.

Second string after a fill
Shot……..Velocity (f.p.s.)
1……………..834
2……………..831
3……………..825
4……………..819
5……………..814
6……………..807
7……………..800
8……………..791

The average for this string is 815 f.p.s. That works out to 37.46 foot-pounds. The total spread is 43 f.p.s. That is what I expected — both from the results seen in the first string and also from the targets shot at 50 yards on 2 different days. This is what I have to address to get the rifle more consistent.

Rather than selecting a desired velocity out of thin air and working to achieve that arbitrary number, I choose to work with what the rifle seems capable of delivering. At this point no adjustments have been made, but now they will begin.

First question — is my rifle maxed out as it came from the factory? To get more velocity I need more air — it’s a simple as that. But — and this is very crucial to understand — there are two things that control the airflow. The length of time the valve remains open is one, and that is controlled by the striker spring tension. The amount the air transfer port is open is the other. Both things have upper limits, so I need to find out where the rifle is right now.

Early hiccup!

The first thing I discovered is that even through the RAI stock folds to the side, providing access to the striker adjustment screw through a hole in the stock adapter, I did not have a 1/8″ Allen wrench long enough to reach through to the screw head. So, the entire RAI modular stock had to come off the gun. If I was going to adjust the striker spring a lot I would get a longer wrench, but once I get it adjusted where I want, I’m going to leave it alone.

Striker adjustment 1

I then turned the striker adjustment screw in 8 full turns. I was looking for the stop, but after 8 turns I decided to check the velocity. The rifle was filled to 3000 psi and here are the shots.

Shot……..Velocity (f.p.s.)
1……………..485
2……………..493

Striker adjustment 2

Obviously this wasn’t where I wanted to go. So I turned the screw out again until it was 1-1/2 turns in from where it was from the factory. I then finished the string of 8 shots.

Shot……..Velocity (f.p.s.)
3……………..792
4……………..792
5……………..792
6……………..798
7……………..795
8……………..798

This was almost exactly where I was hoping to be with this pellet! I reloaded the magazine and fired the next 8 shots.

Second string after a fill
Shot……..Velocity (f.p.s.)
1……………..800
2……………..802
3……………..802
4……………..804
5……………..805
6……………..808
7……………..807
8……………..808

This was looking very promising! The velocity was increasing, but at a very slow pace. So I reloaded and shot the third magazine of 8.

Third string after a fill
Shot……..Velocity (f.p.s.)
1……………..810
2……………..805
3……………..805
4……………..808
5……………..806
6……………..803
7……………..801
8……………..799

This is wonderful. I am now getting 24 shots on one fill with a maximum velocity spread of 18 f.p.s. Well, I can’t say that for sure, because the first 2 shots were with the striker adjusted differently. But at least 22 shots were achieved. However, I was inclined to adjust the striker once more and very slightly. I turned the striker adjustment screw out 1/4 turn and recorded the following.

First string after a fill
Shot……..Velocity (f.p.s.)
1……………..778
2……………..786
3……………..790
4……………..785
5……………..786
6……………..808
7……………..790
8……………..797

Second string after a fill
Shot……..Velocity (f.p.s.)
1……………..796
2……………..798
3……………..800
4……………..802

STOP

I stopped because the velocity had risen to the place I was after. Now I wanted to find out how much air was in the rifle, so I connected the air tank and opened the valve. The needle on the tank gauge stopped rising at 2500 psi. There was 2500 psi in the rifle!

Change of plans

I was running on a 2500 psi fill at this point. If I could get enough shots at my desired velocity, this was where I wanted to be. So I started recording the velocities again, this time from a fill of 2500 psi.

First string after a 2500 psi fill
Shot……..Velocity (f.p.s.)
1……………..799
2……………..803
3……………..803
4……………..804
5……………..808
6……………..799
7……………..811
8……………..808

Second string after a 2500 psi fill
Shot……..Velocity (f.p.s.)
1……………..807
2……………..808
3……………..807
4……………..808
5……………..802
6……………..803
7……………..802
8……………..801

The next shots after this second magazine were:

Shot……..Velocity (f.p.s.)
1……………..801
2……………..796
3……………..793
4……………..788

The rifle’s performance with this adjustment

My .25 caliber Marauder now gives me 2 complete magazines (16 shots) with a little extra on a 2500 psi fill. The average velocity with the JSB King pellets is 804.6 f.p.s., which produces 36.51 foot-pounds. I’ll take that and smile! The maximum velocity spread is just 12 f.p.s. I’ll also take that!

Yes I could get more power from this rifle and I could probably get 16 good shots at the same time. But not on a fill to 2500 psi. That’s what I want, because it’s all the power I need and I’m saving a lot of air.

A final benefit is that the rifle is MUCH quieter at this reduced velocity. I guess it was wasting some air before. I can’t wait to get back to the 50-yard range and see what this adjustment has done for accuracy.