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Accessories Benjamin Marauder PCP .177-caliber air rifle: Part 6

Benjamin Marauder PCP .177-caliber air rifle: Part 6

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Secrets of loading the Benjamin Marauder magazine
Part 3
Part 4
Part 5

Benjamin Marauder
Benjamin Marauder

Today, I’m going to attempt to correct the accuracy problem I created in the last report, where I reduced the average velocity from 1015 f.p.s. to 886 f.p.s. in the Benjamin Marauder while testing with Crosman Premier 7.9-grain pellets. The best group at the higher speed was 10 shots in 0.285 inches, center to center, at 25 yards; but at the new lower velocity, the best group was only 0.397 inches between centers. I was hoping to get approximately the same group size — around 10 shots into 0.30 inches at 25 yards at the lower velocity. When that didn’t happen, I had a decision to make. Should I continue with the other things I wanted to do, or should I fix this one first? I decided to do what I would have done had I not been testing the rifle for a blog, but just for myself. I decided to get the accuracy back on line.

Once again, I removed the barreled action from the stock and got access to the power adjustment screw on the right side of the receiver. To see where this is, read Part 4 of this report.

I turned the power screw another 1/3 turn counterclockwise, bringing the total adjustment to 2 full turns out from all the way in. Remember that when we began this test, I discovered that the power screw was adjusted 2-1/3 turns out, so we are now 1/3 turn shy of that.

Then, I fired 10 Crosman Premier lites. I was concerned that the first shots might not be up on the power curve because we found in Part 4 that the first 2 shots were below the desired speed when the rifle was filled to 3,000 psi. Here are the shots as they occurred:

Shot   Vel.

*Fastest shot
**Slowest shot

Average velocity 955 f.p.s.

It seems like I hit the desired velocity on the first try. I locked the power screw and put the action back into the stock. I had now fired 10 shots on this fill; and from all the previous testing, I knew there were at least 20 more good shots available — and probably several more. I decided to shoot 2 groups of 10 shots each at 25 yards.

Group 1
The first group from 25 yards put 10 pellets into 0.268 inches. That’s slightly smaller than the best group at the highest velocity. Of course, I didn’t know that while I was shooting, so I continued to shoot group 2.

Benjamin Marauder group 1
Ten Crosman Premier lites went into this 0.268-inch group at 25 yards. It’s well-centered and just high enough to miss the aim point on the target.

Group 2
Group 2 is larger than group 1. It measures 0.327 inches between centers. In light of group 1, however, I feel this is not so bad. I had larger groups at the higher power, too.

Benjamin Marauder group 2
Ten Crosman Premier lites went into this 0.327-inch group at 25 yards. It’s also well-centered and a little more vertical than the first group.

What if…
After shooting the second group, I thought about the reader comments I might get when I published this report. Comments like, “Why did you stop after group 2? Are you sure the rifle wouldn’t continue to shoot good groups, even though after 30 shots it will probably fall off the power curve at some point?” So, I shot a third group just to see what would happen. Those 10 shots went into 0.416 inches.

Benjamin Marauder group 3
Ten Crosman Premier lites went into this 0.416-inch group at 25 yards. I feel fairly certain that some of these shots toward the end were off the optimum power curve.

At no time during this shooting were any shots called pulls. All shots went off with the crosshairs on the 10-ring (dot) of the target as they should have been. All pellets were straight from the box with no sorting of any kind. So this test was conducted exactly as I would shoot the rifle at any given time.

I now feel the gun is shooting as I want it to. The next step will be to adjust the fill pressure level so the rifle can be filled to a lower pressure and still operate at this velocity. I’ll probably have to adjust the power screw again as I adjust the rest of the firing mechanism to keep the gun shooting at this velocity. The purpose of that exercise will be to see how many good shots are in a string at a lower fill pressure and to see if it’s worthwhile to lower the fill pressure.

Shot counter
One last thing before I end this report. I haven’t yet commented on the shot counter that’s built into the Marauder magazine, but it’s there and it really works well. I haven’t ever used shot counters like this in the past because I’ve always found them clunky and difficult to see.

Benjamin Marauder magazine shot counter
The shot counter is a circular window on the right side of the magazine — the side that sticks out away from the rifle. The number in the circle indicates the number of pellets that have been moved from the magazine into the breech of the barrel. It doesn’t tell you if that shot has been fired yet, but you should know that.

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.

46 thoughts on “Benjamin Marauder PCP .177-caliber air rifle: Part 6”

  1. Last night, after our normal 25 yard Bullseye competition, we had a .22 rifle bench rest competition. I decided to use my .22 Marauder with my repaired magazine (hope to do a blog on this shortly). The competition was at 25 yards (limit of our range facility) and consisted of 5 rounds at 5 targets each with one sighter on one sheet of paper. I assume these targets were NRA regulation. Long story short, I shot a 42 out of a possible 50 (no refilling needed). Top score was 48 and three more of my fellow competitors had higher scores than me (out of 12), all shooting rimfire rifles – from Anschutz’ to level action Savage and breathed on Ruger 10/22’s. I promise I’ll do better next time for the honor of the blog!

    Oh, Victor – I achieved my highest score yet in the 25 yard Bullseye competition – 207. I’m getting there! More trigger control needed!

    Fred DPRoNJ

    • Fred,

      That’s great! Trigger control is a key element of the overall set of fundamentals and yet separate from the goal (The Cardinal Rule) in that it requires very specific attention and solution finding.

      Yes, you are getting there! You’ve broken the barrier of 200, and are now climbing over it to the point where it is clearly not luck. Because you set a specific goal to achieve, and have achieved it, you are proving that you are developing real skill. That is a personal accomplishment that you should be proud of. Shooting is truly an individual sport, so each individual has to overcome and conquer their own specific weaknesses. You know what they are, and so you know what to focus on.

      Great job!

      • Matt,

        for this particular competition, the max one could do was 50 – 5 targets with 5 rounds per target. To make it simple, we started off with a max of 10 and subtracted if a round was outside the 10 or X ring. So in one target, I had 2 nines (2 points off) for a total of 8 for that target. One target had a 7 (I knew I should have shot one or two more sighters to let the Marauder valve settle in!) and 8 so 5 was subtracted (two for the 8, three for the 7) and one target had a nine ring so 1 was subtracted. Add those up and I lost 8 points out of a perfect 50 (other two targets were perfect but that wasn’t good enough).

        Fred DPRoNJ

  2. That’s impressive. This is what I have worked real hard to get my discovery to do. So far it’s keeping pace with your Marauder. If I find it falls short I pull it apart and figure out why it isn’t at the Marauder standard. When I learned the Marauder had adjustable power I put in a power adjuster. When I found what the marauder could do in .22 I tore apart my Discovery and rebuilt the guts of the thing with all new custom valving. Only thing I need to do now is install a debounce device and a tko22 muzzle device to quiet the thing down. The reason I am modifying my Discovery like this is for several reasons. First the Marauder is hard to get in Michigan with its shrouded and baffled barrel. Second I like the slimmer Discovery, third I like the challenge, and fourth, I don’t see going through the expense to buy a Marauder when I can make a discovery perform just as good. I have way too many guns and don’t use what I have half as much as I should. But I do like the Marauder the more I look at it.

  3. It’s always gratifying to hear about the Marauder. A shot counter for a pcp is probably not critical since there is no harm in dry-firing, but it certainly is for my IZH 61. I really did not appreciate how hard it was for me to count to 5. But there is a sort of makeshift Russian style counter in that when the clip shows three holes exposed on the side, you know you are on your last round. It works pretty well.

    B.B., no way. So you meant rotating about the axis of the scope the other day? But… I know that it is a seriously annoying problem to get the reticle perfectly level, but this involves fractions of a degree of rotation. You mean that the elevation and adjustment knobs are rotating the internal scope tube around its long axis? I wouldn’t think that would accomplish anything since the cylinder shape is symmetrical around this axis. Well, at least I know what rotation you’re talking about. I will continue to think about this.

    Is optical centering the same as having your scope in the middle of its adjustment range? If so, could you achieve the same thing by experimentally finding the maximum range of adjustment for both elevation and windage, dividing by 2, and counting yourself there from one extreme?

    Thanks for the info about the Russian scope which I understand perfectly. As Wulfraed shows, my inverse procedure was inverted. Instead of adjusting from point of impact to point of aim, you go the other way. There is a YouTube demonstration that showed how this way of zeroing can be very fast. It was much faster than the method for the Mauser sniper rifles which worked like our scopes except that the adjustments had to be done with wrenches. German engineering does have its little lapses that often go with being overly ingenious. On my k98, the sling is very complicated and in allowing you to carry the rifle a little more comfortably on the side, it gets in the way in the shooting position. I also find that unlike both the Enfield and the Mosin, the length of pull is just a little too short for me to keep the cheekweld. It’s a fine piece of equipment, but it has the little irritations.

    Victor, thanks for the info. Yes, beginner’s luck and even talent can turn out to be liabilities in leading people away from the path of the daily purposeful practice.


    • Matt,

      I find that I have a hard time counting to 5 too… After much research into the matter, I’ve concluded that it is because all of my fingers are busy shooting at the moment. So really, keeping track of any greater number than 1 is just pure luck….


  4. B.B.
    I’m new here, with an M-rod in .22, so I find everything educational.
    However, I have a very short in town back yard and want to charge the weapon with CO2, so the rounds don’t go too far over the fence.

    If you should ever get a chance, the documentation hints at all the adjustments but nothing specific.

    Thank you

    • Hi, Dritter. Welcome! If you’re looking for lower velocities out of your Marauder, you don’t *need* CO2 to get there. You can probably choose your “fuel” based on the convenience of fills. I haven’t tried my m-rod on CO2, but using air, the transfer port adjustment can choke the thing down about as far as you like! And when you restrict the transfer port to achieve lower velocities, you will find that you get tons of shots, with *lots* of consistency! That’s one tidbit that we perhaps haven’t discussed much yet in this series.

      E.g., on my .177 m-rod, starting at an arbitrary ~850 fps baseline (already well reduced from factory power), one turn in on the transfer port drops me to ~540 fps, with *very* little noise. Another half-turn back out from there lands me at 690 fps, +/- only 1 fps over 10 shots. I didn’t chronograph extended strings at these velocities since I was shooting for 11.5 fpe, but I’m reasonably sure you’d get *hundreds* of good shots at these low speeds.

      Another 5/16 turns from 690 fps lands me at my 11.5 fpe target, right around 785 fps with the JSB 8.4’s. At this velocity, I have 48 shots within 2%, and a whole bunch more with wider tolerances. I use the 48-shot figure for Field Target (meaning I refill about halfway through a 60- or 72-shot match, give or take), and I count it as 80 or 90 “plinking grade” shots before refilling.

      Anyway, if you have a convenient source of high pressure air, you might find that you get just as many low-power shots on air as on CO2, and you will probably get much more consistency on air, without all the temperature fussiness.


  5. B.B.
    Yes, not much else. Once I open the needle valve and tweak the hammer, not much to do for 800lbs or so. Just many of the ‘same’ shots till all the liquid turns to gas (or so I suspect) since the pressure is consistent from shot to shot. Or so they say..

  6. I have a Discovery w/TKO muzzle brake and like it a lot. That being said, I really like Marauder better. THAT being said, I’m still waiting for the new synthetic stock Marauder with the adjustable comb, lighter, thinner stock, and different geometry regarding trigger and grip placement. They were looking at a July roll-out, but I just got an email from them saying that they are now HOPING for a September or October date. So I guess I’ll be discoing for the foreseeable future, any relying on Santa to fill my PCP dreams. And keeping my Discovery unmarred and stock, ready for resale whenever.

    • Essbee,

      The size (air capacity) of the tank is irrelevant. A 6 cubic foot tank and an 80 cubic foot tank that both have K-valves (which the tank you linked to has) will connect to the same things and will provide the same output. Obviously the smaller tank does hold less air.

      What you need is a hose to connect that tank’s K-valve to the male Schraeder valve nipple on the Marauder. Pyramyd AIR has such hoses like this one:



  7. But the hoses and connections are too expensive at Pyramidair. May I take your advice on whether I should buy the pump that is about $180. I was interested in this small tank for PCP. But if the tank $100 and $130 for hoses makes it $230 what is the point. Would I be fine with the hand pump? How many times would I have pump to reach 300 bar? What are maintenance issue do we have to replace the washer and how much it costs. Thnx.

    • Essbee,

      The Marauder only fills to 200 bar. No hand pump on the market will fill to 300 bar. Since you never shoot the gun empty, it will take about 75-100 pump strokes to refill the gun, depending on the pressure level you have the gun set for. You can change that to suit yourself, within reason.

      If saving money is a factor, then, yes, the hand pump is a good way to go with a Marauder.


    • Essbee,

      The Marauder pre-packaged deal includes a Benjamin hand pump. The Air Venturi hand pump is not the same. The Marauder hand pump says it can pump up to 3,600 psi, while the Air Venturi hand pump can deliver up to 3,335 psi.


  8. Thanks. How does The Benjamin Marauder compare with German guns (RWS & Weihrauch) in terms of quality and durability and ease too. No doubt the Germans are pricey in PCP hence ruled out but their quality is no problem. Could I have a report for or against on the quality of Benjamin Marauder as compared to German technology and craftsmanship.

    What are the chances the gas will leak on PCP guns. If it does how will it be fixed and at what cost? In contrast the air springers have no such problem. What do you say on this? What is the record at your end of PCP repairs vs air springers?

    Hence I was comparing an RWS 34, RWS 350 Magnum and RWS Air King 54. Considering the cocking effort, weight and velocity it seems RWS 34 stands up very well in .22 with longer barrel. Am I correct? For hunting which is the best?

    • Essbee,

      The Marauder is every bit as well-made as those German PCPs, and it is far more advanced in how it works and the adjustability.

      Yes, PCPs do leak sometimes. And spring guns break their springs. Everything breaks sometimes.

      The RWS Diana 34 is a wonderful air rifle for hunting. It’s accurate, easy to cock and the trigger is quite nice.

      Your questions seem to come from the standpoint of wanting to get into airguns in a big way and not being sure of what is good and what isn’t. I am going to make tomorrow’s blog just for you — and for everyone else in the same position who isn’t writing in.


  9. Thanks. I also considered RWS 48 (liked it) and HD 90 and HD 80. My criteria is a light one, not loud, long barrel not a long gun, easy to cock yet powerful. In my childhood days I used a Diana 35 (model 1965) which had all the features. I had bought a Gamo 1000 Shadow some years back. It was loud and hard to cock. I mean after a while you felt tired. I was never tired with my Diana 35 yet it was ever so effective. So thought to go back to my old brand. BTW I also have an Weihrauch HD 80 but it was heavy with a scope. then found a marauder in your arsenal.

    Last year I had bought a Walther Dominator for a friend, came from Pyramidair, It had every thing, that special scope with a wheel and bipods, two magazines and every thing. But it was too very heavy in the end. So discounted it. So I want it simple. Light. Quite. Powerful. Ease of use. These days cost is also a factor for me. So I had thought a Diana 34 can be in the boot on weekends and do my job in the seasons.

    Sorry whenever I buy something I research and study a lot. Like I want to buy a new camera research is going on in full swing. Although I have lots of Nikons and Canons. Technology changes I want to be abreast of it.

    I must pay a compliment to Pyramidair which I have been following for a long time and I have learnt a lot from it. Thank you Pyramidair for the knowledge you give through your site, blog and videos which I am so fond of.

    • Essbee,

      This is a blog and not directly connected to the Pyramyd AIR sales department. But I can tell you that if anyone has a Diana 35 mainspring it will be Pyramyd AIR, because they bought up all the new old stock parts for vintage airguns.

      Call their sales department to inquire.



    • Consider though, that if the tanks are rated for, say, 3000PSI max, and the PCP is also being loaded to 3000PSI — the first load from the tank will result in both being just a hair under 3000PSI. And subsequent loadings will be even lower.

      OTOH: if you are loading to, say, 2700PSI max, then you might get maybe six full 2700PSI loadings before the tank drops below that (I’m assuming a 50PSI drop in the tank with each loading).

      This is where the glass-fiber reinforced 4500PSI tanks are nice, when used with PCPs loading to 3000PSI or less… You get a lot of reloads before hitting the point where both tank and gun will be getting lower and lower on each loading.

      Common aluminum 3000PSI SCUBA tanks are normally used (for diving) until they are down to a few hundred PSI (basically, as long as they can provide a regulated air pressure matching the pressure of sea water on the body — and for shallow dives that isn’t all that much). But for a PCP, where we want to load to that 2700PSI for example, we’d be taking in a tank for refill at a stage where a diver would consider it still full.

  10. You have explained it beautifully Sir. Grateful. But considering the cost of the tanks and filling I better give up on tanks and go for the pump which is also around $180. I hope that lasts for while. Are their any maintenance issues or failures in the pump?

    • Essbee,

      Are there pump failures? Oh YES! Are they a maintenance problem? Absolutely!

      I recommend ONLY the Hill pump at this time, until the Benjamin butterfly pump comes out, then we’ll see.

      A pump is not the place to try to save money.

      And if you get one — KEEP-A your hands off it except to use it! NO Maintenance! The worst thing you can do is to try to repair a hand pump if you don’t know what you’re doing and have all the right parts.


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