Benjamin Marauder PCP .177-caliber air rifle: Part 7

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
Part 6
Fixing a Marauder magazine

Benjamin Marauder
Benjamin Marauder

Today, we’ll adjust the Benjamin Marauder PCP air rifle to accept a lower maximum fill pressure and still deliver about the same velocity as before. Before we get into the report, let’s consider for a moment what we’re about to do. As far as I know, the Marauder is the only PCP on the market that allows this kind of adjustment to be made. A great many PCPs have adjustable power, and indeed, the Marauder’s adjustment process for power has been sharply criticized on the internet…mostly by people who don’t appreciate how it works in conjunction with this other adjustment that’s unique to this rifle.

Most other PCPs adjust their power by changing the tension on the striker spring. The Marauder does it by reducing the airflow through the transfer port. What you get from that is far more control over the adjustment, plus it allows for the other adjustment — the one we’re about to do today. And the Marauder is the only PCP on the market with this facility. Criticizing how it works is akin to criticizing a thoroughbred horse because there’s dirt stuck to one of its hooves! At least that’s my opinion.

Why adjust the maximum fill pressure?
This is such a unique feature that a lot of readers who are not yet shooting precharged airguns must be asking why anyone would want to adjust the level of the fill pressure in a gun. Let me make a quick analogy, then I will explain it in detail. Imagine you own a sports car that operates on premium gasoline. There are a lot of cars like that, but your car is very special because it has a switch on the dashboard that allows you to adjust the engine to operate perfectly on low-octane gasoline. It won’t go as far on a gallon, but it will go just as fast. That’s the equivalent of what the Marauder gives you with this fill-pressure adjustment.

Anyone who uses a hand pump to fill their rifle will appreciate the ability to reduce the maximum fill pressure from 3,000 psi to something lower. Hand pumps become hard to operate somewhere above 2,000 psi. For me, it happens around 2,500 psi, but it’s different for every person. If I can reduce the maximum fill pressure from 3,000 psi to 2,500 psi and still get a reasonable number of shots, I’m golden. Sure, I won’t get quite as many good shots (remember that my definition of a good shot is one that stays within about a 30 f.p.s. band of velocity) at 2,500 psi as I would at 3,000 psi; but if I can still get a decent number, that’s all I want.

Reason No. 2 for wanting this feature is the person who lives 25 miles away from the closest dive shop and only owns one 3,000 psi scuba tank. They’ll get only one complete fill from a freshly filled scuba tank and then the rest of the fills will be less than full. But if they could lower their rifle’s max fill to just 2,500 psi, imagine how many more full fills they’ll get from the same scuba tank.

I’m conducting this test exclusively with Crosman Premier lite pellets, as I want a super-accurate pellet and this one has been proven in past testing. I also know that if this pellet goes around 955 f.p.s., it’ll be most accurate.

Let’s go!
I told you that I’d talked to Crosman and gotten some good advice about what I’m about to do. That advice follows. There are 2 separate adjustments we will be making today, and we may also have to adjust the airflow (power adjustment) like we did before. That’s a possible 3 adjustments in all. The manual reads like you can make just one adjustment or the other and get what you want, but Crosman told me not to do it that way. I’ll be adjusting both the striker spring tension and the length of the striker stroke. And, by the way, the Crosman manual uses the terms hammer and striker interchangeably, but I’ll use just the term striker today since that’s what it really is. A hammer is pivoted on an axle, while a striker travels in a straight line.

08-22-13-01a-Benjamin-Marauder-striker-spring-adjustment
Both the striker spring tension adjustment and the striker stroke length adjustment are accessed through a hole at the back of the receiver. This 1/4-inch Allen wrench adjusts the striker spring tension (out, for less tension). This screw is hollow to allow a 1/8-inch Allen wrench to pass through to the striker stroke length adjustment screw (in, for a shorter striker stroke).

We know at the start of this procedure that the rifle accepts a fill pressure of 3,000 psi and gets about 32 good shots (within 30 f.p.s.) before needing a fresh fill. The average velocity is currently 955 f.p.s.

I want to adjust the gun to accept a maximum fill pressure of about 2,500 psi and keep roughly the same velocity. Then, I’ll count the number of good shots I get with that fill pressure and we’ll see if it’s worth changing the gun this way.

Adjustment first
I turned the striker spring tension 2.5 turns out (taking tension off the striker spring), filled the rifle to 2,500 psi and started shooting.

Shot—Velocity
1—926
2—930
3—927
4—924
5—924
6—920
7—919
8—918
9—910
10—913
11—916
12—912
13—911
14—911

After these shots, I could tell the rifle wasn’t going to shoot any faster, so I decided to adjust the power screw. That’s the screw located on the right side of the receiver. I backed it out 1/3 turn, bringing the rifle back to the original power adjustment position, but that was back before I’d adjusted the striker spring tension. I knew the gun should get faster at this setting, but I hoped it wouldn’t go all the way back to the 1,020 f.p.s. average it was initially.

Then, I filled the rifle to 2,500 psi and started testing it again.

1—989
2—991
3—994
4—993
5—991

This was a bit too fast, so I wanted to dial back some of the power. Instead of the power screw, I was now adjusting the striker spring tension and the striker stroke length.

Striker stroke turned in 1/4 turn (lowers velocity).

6—992
7—994

Striker stroke turned in 1/4 turn (lowers velocity).

8—993
9—988

Striker stroke turned in 1/4 turn (lowers velocity).

10—987
11—987

Striker stroke turned in 1/2 turn (lowers velocity)

12—984
13—982

Striker stroke turned in 1/2 turn (lowers velocity).

14—977
15—975

Striker stroke turned in 1/2 turn (lowers velocity).

16—966
17—975

Striker stroke turned in 1/4 turn (lowers velocity).

18—968
19—974

Striker stroke turned in 1/2 turn (lowers velocity).

20—958
21—958
22—971
23—967
24—970

Striker stroke turned in 1/2 turn (lowers velocity).

25—959

I’ll stop here and discuss what happened. If you add up the adjustments to the striker stroke screw, you’ll see I’ve adjusted it in 3-1/2 turns at this time. That makes the length of the striker stroke shorter, which allows the valve to open and close in a shorter amount of time. Less air gets out.

I’m pretty confident that the maximum fill pressure is now considerably lower than 3,000 psi. To test that, I filled the reservoir to 2,800 psi and started shooting.

Shot—Velocity
1—799
2—851
3—859
4—871
5—878
6—866
7—882
8—891
9—896
10—902

Okay, since the velocity is rising, it’s obvious that 2,800 psi was too high a fill pressure. The rifle is probably now near the max fill pressure range we wanted. That’s a guess that will have to be tested.

Shot—Velocity
11—900
12—895
13—914
14—917
15—922
16—923
17—931
18—934
19—919
20—932 (2,000 psi end pressure)

At this time, I stopped and refilled the gun to 2,500 psi. It was at 2,000 psi after shot No. 20, so I’m pretty sure the power’s peaked at this point. I now adjust the striker spring tension in by 1/4 turn. That puts more tension on the spring, and the valve gets hit harder.

Shot—Velocity
1—901
2 904

That’s not enough of a power increase. So I turned the striker spring tension in another 1/4 turn.

3—905
4—914

That’s still way less velocity than I wanted to see. I backed out the striker stroke length screw 1/2 turn, making the striker stroke longer.

5—928
6—939
7—949 (first shot on the power curve)

Now the velocity appears to be up where I’d hoped to get it. I’ll continue to shoot this string, not filling the gun since the last 2,500 psi fill.

8—956
9—950
10—956
11—961
12—962
13—960
14—967
15—960
16—959
17—965
18—965
19—963
20—964
21—964
22—964
23—960
24—958
25—958
26—958
27—954
28—953
29—952
30—949
31—949
32—950
33—946 (off the power curve)
34—936

There were 26 shots that ranged between 949 f.p.s. and 967 f.p.s. The total spread was 18 f.p.s. That’s a lot tighter than the 30 f.p.s. I talked about at the beginning of this report, but the power seems to be dropping off pretty fast. But the question is: Are we at the target fill pressure yet?

To learn that, I filled the gun to 2,500 psi and shot the following:

Shot—Velocity
1—969
2—957
3—952

So 2,500 psi works fine. I then refilled the gun to 2,600 psi and shot the following:

Shot—Velocity
1—937
2—934
3—949

I have narrowed it down to the point that 2,500 psi is okay and 2,600 psi is a little too much. That’s it for me. The rifle is where I wanted to get it.

I now have a rifle that gets an average velocity of 955-958 f.p.s. with Crosman Premier lites and gets 26 good shots on a 2,500 psi fill. If I fill to 2,500 psi and shoot just two full magazines, I know I’ll get all my shots at the most accurate velocity this rifle is capable of producing with this pellet.

By adjusting the maximum fill pressure back to 2,500 psi, we lose 6 good shots (compared to the 32 good shots it got with a 3,000 psi fill) but are able to remain at exactly the same power level as before. If a person wanted to fill to a lower pressure, this seems like an effective way of doing it.

This entire procedure took me about 3 hours to complete, and I would say I was somewhat lucky — though I did some things that helped my luck by adjusting both the striker stroke and the striker spring tension instead of trying to do it all with just one or the other. I also turned up the power screw at one point because I could see the rifle needed a little more air to get up to the velocity I was seeking.

Will you be this lucky? You may be if you follow the procedure I’ve explained here. I can’t guarantee that you’ll be, but I do know the way I did it is the way Crosman recommends.

30 Responses to “Benjamin Marauder PCP .177-caliber air rifle: Part 7”

  • RidgeRunner Says:

    Fill pressures seem to be following velocities with marketeering. As you have illustrated, yes you can get more shots with higher fill pressures, but do you really lose that many at lower pressures?

    I do have to concede that with the big bores, you do need more air. But even then you can set things up so that the fill pressure is real low as long as you balance it with a larger volume of air (valve staying open longer). Also, you will likely need a longer barrel to allow time for that larger volume of air to bring the slug up to speed.

    Now if your PCP is regulated, you want the highest fill pressure you can get. My Edge is fantastic. Fill that tiny tank to 3000 PSI and I can shoot until I am tired of shooting. My TSS valve operates at 1800 PSI. I am seriously thinking of a regulator for it.

    You CAN adjust just about any PCP to operate at lower fill pressures, but in most cases that will require disassembly of the PCP and some mechanical engineering skills or dumb luck.

  • Bub Says:

    Why do you need to adjust fill pressure, especially when using a hand pump? Would you not get the same result just stopping at 2500 psi range?

    • twotalon Says:

      PCPs are designed to operate with satisfactory results within a certain pressure range. If you try to run them outside these pressure limits, they fall on their butt.
      B.B. is showing how you can tune the rifle to get it to operate within the limits that you want.

      twotalon

    • B.B. Pelletier Says:

      Bub,

      If you just filled the gun to 2,500 psi when it was set up to be filled to 3,000 psi you would get about half the shots (32 = 16), instead of 26 good shots. What I did here gave me many more shots at the same power, but with a lower fill pressure.

      Good question!

      B.B.

  • FrankBpc Says:

    First off BB,I do hope your cut heals up quickly (just like it happened).As a sharpening nut my biggest fear is things like that happening when I turn over crazy sharp knives to their owners.
    Thank you for caring about correct terminology,the use of the term “hammer” seems to be everywhere in PCPs.The relationship between the relatively few parts of a PCP system are a lot to take in,but between you & Lloyd Sykes I have become much more comfortable with them.The Marauder,aside from being an excellent shooting tool….is like a science lab in a wood stock! My urge to acquire one is growing.You are a supreme “enabler” once again…LOL (for some bizarre reason,the answer is already in the verification box??? I knew this one too! 4+?=5)

    • Matt61 Says:

      Yes, I read an account by one sharpening firm where they sharpened some guy’s knife at a fair, and when he put it back into the sheath, it went right through the sheath… I got their product, but it didn’t perform like that.

      Matt61

      • FrankBpc Says:

        Send it my way Matt,and when it comes back it will…..unless the sheath is Kevlar.

        • Slinging Lead Says:

          Frank

          What is this “pc” stuff? I never received your notarized handle change requisition notification.

          • FrankBpc Says:

            Had a premature senior moment brother.My laptop is giving me trouble,so it dumped all the autofill
            content.I accidentally used my YF username…….the “pc” suffix was necessary because Frank Barrecca
            had “dibs” on my FrankB! Two Italians that use Frank B…….who’da guessed that! LOL
            At least FrankBpc is recognizable to those who email me.

  • AlanL Says:

    Hey folks,
    For you collectors out there, I spotted a 1921 Titan air pistol coming up for auction. It’s lot #797 in Lockdale’s Sept 14-15 auction. Check it out on the The-Saleroom(dot)com.
    AlanL

  • Chris Legate Says:

    Thanks B.B.!
    It’s nice to know what my rife is capable of. I love the possibilities of what you can do with this rifle. I see it would be possible (if careful notes are kept) of tuning the velocity and fill ratings to… let’s say shoot in field target at a lower foot/pounds rating. Then if you wanted to go hunting and would like a little more speed? Readjust. Thanks again B.B.!

    • Lee Says:

      In my opinion it is better to have different rifle for hunting and field target competition. Less hassle with adjustment and more reason to buy just one more gun.

  • Doug Says:

    Hi B.B.,

    I have a couple of questions about the new-ish .22 cal Airforce Condor SS PCP Air Rifle with the Spin-Loc Tank:
    1. The Pyramyd Air website says that the Loudness is 4-Medium-High. Is this true? I thought the Condor SS was supposed to be very quiet?
    2. The Condor SS seems to be very hard to come by, at least on the Pyramyd Air website. Is there a shortage of these airguns?
    3. Will they ever make the Condor SS a 10 shot repeater (10rds mag) like the Marauder?
    4. I noticed that a lot of people use high rings with the Condor and the Talon. It seems to be more for getting your eye level over and around the air tank than for scope bell clearance. Do you think I’d need high rings for my Leapers 3-12×44 AO SWAT (30mm tube) scope?

    Thank you,

    Doug

    • Edith Gaylord Says:

      Doug,

      B.B. is at the range right now. I can answer some of your questions, but I’m sure B.B. will chime in when he gets back:

      1. The Pyramyd Air website says that the Loudness is 4-Medium-High. Is this true? I thought the Condor SS was supposed to be very quiet?
      It IS louder than the Talon SS but not as loud as the unbaffled Condor. There’s a blog post about this Condor SS rifle, and it addresses the fact that it’s quite loud. When B.B. shot it inside our house the first time, I assumed it was an unsilenced gun. It echoed off the walls with ferocity. It took me and the cats totally by surprise.

      2. The Condor SS seems to be very hard to come by, at least on the Pyramyd Air website. Is there a shortage of these airguns?
      I wouldn’t say there’s a shortage. But I would say that the demand for the gun may have caught AirForce by surprise. I bet they’re working 24/7 making more guns.

      3. Will they ever make the Condor SS a 10 shot repeater (10rds mag) like the Marauder?
      You’re certainly not the first person to request a repeating AirForce rifle. Airgunners have been asking for years. If/when that ever happens, there will be a lot of people dancin’ in the streets.

      4. I noticed that a lot of people use high rings with the Condor and the Talon. It seems to be more for getting your eye level over and around the air tank than for scope bell clearance. Do you think I’d need high rings for my Leapers 3-12×44 AO SWAT (30mm tube) scope?
      I think the issue is as you stated it…getting your eye to the right level.

  • Matt61 Says:

    So, is there a reason why the adjustment procedure is so much more difficult than for Wayne’s S410 or the Air Force rifles where you turn a dial? Wayne made that sound pretty appealing.

    Matt61

    • B.B. Pelletier Says:

      Matt,

      This is the only rifle in the world that allows you to adjust the maximum fill pressure. Because of that, the power adjustment has to be a little more complex than one of the simpler European rifles. But the Marauder is a whole heck of a lot more flexible, too.

      B.B.

  • Matt in NCAA Says:

    I love my .22 maurader, I spent about 4 weeks tuning and trying different settings with a borrowed chronograph. My wife was glad to see the chrony go back. On a 2800 psi fill I get 30 shots with about a 20 fps spread. The velocity is 814 start 835 in the middle and back 805 at the end using 21 grain barracudas. My adjustments are 3 turns in on spring, 2 in on striker and 3 in from all the way out on the velocity screw. The most important adjustment too me was choking down the transfer port as the more in it went the flatter the string got while still maintains the velocity I needed for hunting. 2800 psi down to 2100 psi.

  • Wulfraed Says:

    There are a lot of cars like that, but your car is very special because it has a switch on the dashboard that allows you to adjust the engine to operate perfectly on low-octane gasoline. It won’t go as far on a gallon, but it will go just as fast.

    Does Detroit know about this magic button?

    The normal result of stuffing regular into a performance engine will be a reduction in top usable power — as any modern engine should have sensors detecting pre-ignition knocking followed by the computer changing the timing or throttle to reduce the peak pressure/power. So — one is likely to get the same (or even better) fuel mileage using regular with reduced performance.

    The opposite direction just wastes money — Premium doesn’t make a car go faster if the engine doesn’t produce the conditions that would result in pinging with regular.

  • J-F Says:

    Just to be sure, you’re adjusting the fill pressure to 2500psi but you could still fill it to 3000psi but it wouldn’t be the optimal set up right?

    Maybe I haven’t got the hang of it or maybe it can’t be done with my set-up (I have the newly available Ninja air tank with the 2900psi regulated output) I tried filling my airguns and stop at 2500psi but when the valve is opened the air rushes out and first thing I know it’s at 2900psi. I can’t fill more but I can’t seem to be able to fill it less either. Is it me or my gear?

    J-F

    • Slinging Lead Says:

      J-F

      If BB filled the gun to 3000 psi with the current settings the valve would be partially locked up, so the first group of shots would be much lower than desired. You saw this to a lesser extent when he filled the gun to 2800 psi. If he filled all the way to 3000 with the new settings these first shots would be even lower.

      I don’t know what kind of valve you have on your fill set up, but on my 4500 psi carbon fiber tank the fill valve is controlled by a wheel about the size of a US quarter. I can open the valve just slightly so that the gun fills up very slowly. I have never overfilled a gun passed the desired pressure. Perhaps you need to add a valve to your fill set up that allows you to have a finer control over how much the valve is opened.

    • FrankBpc Says:

      JF,when you close the fill valve does the guage stay at 2900 before you bleed the line?? If it really is filling THAT fast…..much of that fill pressure will be heat.Bad for the check valve seals at the gun’s inlet valve.I try to take about 60 seconds per thousand psi to avoid that.Are you looking at the gun’s guage when filling?

      • J-F Says:

        Yes it does say 2900 psi. One tank is for the 1701P and the other is the Hatsan AT44, I usually don’t shoot them down too low so filling is quick.
        I’ll try opening it slower next time.

        Thanks for the answers guys.

        J-F

  • Mark N Says:

    B.B.,

    I have problems with the adjustments of striker pre-load and the throw length migrating from their set positions. Do you have any suggestions. I know that there is a set screw to hold the striker in place but it has to be set pretty tight on my marauder to hod it securely. And of course you have to disassemble the gun to get at the set screw. If it’s too tight you can’t adjust it and if it’s too loose the setting changes.

    The setting on the striker tension changes too. These changes happen from one fill to the next. It’s kind of a PITA to reset the settings every fill. Any thoughts, info or suggestions appreciated.

    Mark N

    • Lee Says:

      Mark, as I don’t own Marauder I can’t say for sure this will work for you. Striker stroke length adjustment on my rifle is held in place by set screw as well, but I inserted very small polyurethane rod, sized for the hole. Friction between the PU and screw adjustment is just enough to hold it from migrating. Maybe you can experiment with inner rubber tire instead of PU.

    • B.B. Pelletier Says:

      Mark,

      No, I don’t have any suggestions. I haven’t encountered your problem with either of my Marauders, so I don’t know what to tell you. Have you adjusted the settings a lot? And has oil gotten onto the screw threads?

      To set things right it sounds like a disassembly and drying of the screw threads might be the only solution. I would then stake the threads of both screws to prevent them from turning easily again.

      B.B.

      • Gunfun1 Says:

        The blue Loctite works good if you have that problem because it can easily be broke free and will hold good (and creates a good air seal). The Loctite comes in different colors for the type of bond you want to create.

        We use it when putting engines together for the drag cars. Hardly anybody that I’m aware of uses staking anymore. I know some people still safety wire their fasteners when building engines.

        When you stake a thread it could mess up the part of something that (Can’t) be replaced.
        We use to do that at work many years ago (staking) but with all the different chemical fasteners available today it would be kind of not good to do it with out the chemical fastener.

  • Gunfun1 Says:

    Mark N
    When it comes to the way my Marauder’s perform I’m kind a little crazy about that or any other pcp gun I have for matter of fact.

    I usually Chrony my guns once in a while just to check. But temperature of your surroundings definitely will contribute to that problem.

    And in my case I know how many turns of adjustment the gun is set at, the fill pressure, type of pellet and fps and fpe wrote down in a log book for each gun. And the temperature it was outside when I chronyed.

    I have not had any adjustments change on my guns. But that doesn’t mean anything about your guns.
    I’m sure the adjustments could drift from their settings.

    The only advice I would give is to document. Because I found my memory some times doesn’t match up with what I thought it was supposed to be. When I go back and check what I wrote down it doesn’t lie.

    Oh and what kind of gun are you referring to ?

  • JeffR Says:

    B.B., I’m planning to use my soon to arrive .177 Marauder for target shooting in the 10 to 25 yard range on CO2 until I can afford the equipment to move to NPA. How does the above pressure/velocity discussion apply to this power source? When adjusting a Marauder which do you select first as a starting point for tuning, the performance characteristics of the gun or the pellet, since as I understand it these interact to affect accuracy and repeatable results across a string of shots.

    • B.B. Pelletier Says:

      JeffR,

      I haven’t tested this, but I think you can safely subtract about 250 f.p.s. from the velocities I got when you use CO2. That’s been the sort of ratio I have observed in the past.

      B.B.

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