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tuning a Marauder for shot count - Advice Please!

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Saltlake58

Member
Apr 9, 2015
2,907
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Utah, United States
Ok, I bought a regulator for my Marauder. I'd like to tune for shot count, with reasonable power, maybe 20 fpe. It's a .22, so looking for around 800 fps or maybe a touch less. Baseline is the 14.3 Crosman Premier Dome Pellet

I've tried the regulator at 2200 PSI, got about 25 shots per fill, 900 fps, so looking for a bit less.

Next, tried about 1500 PSI (was trying for about 1800, but missed on the adjustment.). About 830 fps, 32 shots before it fell off the regulator.

Next, brought it back up to around 1700, made a couple adjustments and got to 820-ish fps, 40 shots.

I've seen YouTube Shooter1721 test the Marauder Field and Target and get about 80 shots per fill which I believe is a bit much to expect, but he estimated that the regulator was 1400 PSI and shooting about 830-ish fps. That's kind of what I'm shooting for. (Pun intended)

So far, the 1700 PSI regulator setting, with Hammer spring, and preload set to zero, Transfer port opened about 4 turns. That's giving about 40 shots, with 820 FPS, which is perfectly acceptable.

Does anyone have experience with different settings? Would a lighter hammer spring help? What are the thoughts?

Many thanks,
 
Hi saltlake58,

when I used jsar TSS(twin spring system) it was the best thing I ever added to my gun. It stops the hammer bounce that the marauder has a lot of which wastes a ton of air each shot. If you want a high shot count I highly recommend the TSS my 25 cal. is getting over 50 shots at 35-45 ft.lbs. depending on which pellets I use and which spring. Speak with Travis at Jefferson State air Rifles he is an expert with the Marauders.

Good luck and have fun,

Jim
 
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I have been tinkering with mine lately and found something interesting. I used to have the b-staley oring buffer in my gen 1 marauder and really liked the results. I bought a used 2nd gen with a huma and a LW barrel. It was set up with a lightweight hammer for 12 fpe and 100+shots. I recently needed to rebuild the regulator and on a whim I put in the bstaley orings and tuned it to around 20 fpe and came up with a 10 shot string with a 9 fps spread and a 1.3 sd. I have the original heavy hammer in and the reg set to around 120 bar. I haven’t tuned for optimal efficiency yet but was blown away by the consistency. It sounds like I am still using extra air but I have only recently began to understand what all the more seasoned members are talking about when tuning for most efficiency. I will try and see what the settings are the next time I can get a minute. Good luck!
 
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I have been tinkering with mine lately and found something interesting. I used to have the b-staley oring buffer in my gen 1 marauder and really liked the results. I bought a used 2nd gen with a huma and a LW barrel. It was set up with a lightweight hammer for 12 fpe and 100+shots. I recently needed to rebuild the regulator and on a whim I put in the bstaley orings and tuned it to around 20 fpe and came up with a 10 shot string with a 9 fps spread and a 1.3 sd. I have the original heavy hammer in and the reg set to around 120 bar. I haven’t tuned for optimal efficiency yet but was blown away by the consistency. It sounds like I am still using extra air but I have only recently began to understand what all the more seasoned members are talking about when tuning for most efficiency. I will try and see what the settings are the next time I can get a minute. Good luck!
Click to expand...

Very interested in the results. Keep me posted please!
 
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the ultimate to squeeze maximum efficiency is

- lightweight hammer

- lightweight valve spring

- open up ports (maximize power), need to be handy with drilling/machining/burr removal

- hammer bounce device, tss, ssg etc

Does the factory tuned F&T mrod use the stock over heavy hammer ?

and importantly to tune the reg to your hammer spring to get a few extra shots even as reservoir pressure reaches reg pressure setpoint and even a little lower

google the tuning guide by Bob Sterne

a good tune can net 10 or more shots past the reg setpoint as the reservoir goes down.

I get around 85-90 shots at 19fpe




 
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My configuration is making a little more energy than your target. Nevertheless, my set up is as follows:

  • Huma at 2000 psi
  • Free flight hammer system
  • Stock hammer
  • Stock hammer spring (+1 rotation)
  • .160" transfer port
  • Lightened valve spring in stock valve
  • Marmont barrel

Roughly 70 shots at an average 823 fps with JSB 18.1 (27 ft-lbs).

1551614158_19298568815c7bc0cea73c52.86254937_shot string image.JPG

 
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So many ways to skin this cat...I'll just go to what I think would be an extreme and you can take it there or meet somewhere in the middle.



90% bore ported = .197" porting (oval @ barrel port, .176" x .226")

Hammer weight = 20-25 gr

Bolt probe = 1.1mm @ the tip (gen 1 style is superior to gen 2 but cannot be flipped to accommodate left sided bolt)

Valve throat = .239"

Light weight valve spring (3-6 lb/in)

1300 psi / 90 bar regulator set point (can go lower but this would be quite optimal for your desired power level of 20 fpe.)

SSG with 2" spring @ 7.7 lb/in (I prefer SSG's over TSS, very easy to DIY...but I use a non-traditional method I find far superior to the typical SSG or TSS)



The above should net (1900 usable psi, max 20 psi per shot) 1900 / 20 = 95 shots, or few over 100 shots ideally..as 1 psi per fpe is generally inefficient at those power levels.



-Matt
 
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You are right, there are many ways to skin the cat. I think my goal is 60 shots per fill. So, I like the thought of setting the regulator around 2000 psi so if I wanted power again, could just retune and don't have to take the reg out. A while back, I bought what I thought was a hammer spring, but when it got here, I realized I'd purchased a lightened Hill Valve spring, so I'll install that.

Here's where I think I'll start

  1. Install the new valve spring
  2. set the Regulator at 2000 PSI as a starting point
  3. Install the Staley HDD, I have al O-Ring kit with the required O-Rings in my posession
  4. Everything else I'll leave stock for the moment. Saving Sheckels for a Dreamline so spending any $$ on Marauder parts will take a lot of convincing.
    [/LIST=1]

    Guns are like Golf Clubs. Each has a different purpose. Kind of like a pitching wedge compared to a driver. This will be my putter, accurate, economy, back yard friendly, silent gun. My Driver will be the Impact and the dreamline will be someting else that I haven't figured out yet.



 
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I just ride my hand tuning two 177 Marauders. The goal was to get a high shot count shooting 10.5 grain pellets around 880fps. Here is the combo that finally work giving a 100 shot string before falling off the reg. First get a Huma reg set at 110bar. Then get a lightweight hammer in the 20gr range. Then go to Hill Airgun and buy the 6lb/inch valve spring and the #262 hammer spring. Put all those parts in and it should work. The reg by itself won't get you there.

In your case you already bought your reg so stay on that path. In the purse of figuring this out one of the guys at the range is a machinist and ran a handful of aluminum hammers weighing 25gr. He made some extra one so we swapped them in to a couple Gen 1 and Gen 2 Marauders with outstanding results. We got 70 very consistant shots with nothing more than the lightweight hammer. The velocity range holding very consistant from 870-885 to around shot 65 then falling off to 860 by shot 70.
 
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It's nice to know that what I'm trying to do has been and can be done. I think the champion for shot count on a Marauder was Tom Holland. Granted, he replaced just about every part in the gun with lighter and more precise parts, but at one point, he tuned it down to around 6 FPE, and got 300 shots before it fell off the reg. I'll be happy with 60 or even a little less. This is a nice exercise for a snowy nasty weekend, like this weekend.
 
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Did this back in 2016. Gen2 22 cal. Still have the gun but pulled the reg. I like the higher power so it runs 45+ all the time now. Many ways to skin the cat.

https://www.gatewaytoairguns.org/GTA/index.php?topic=103892.0

End result with 3000psi charge and reg set at 1550:

21.14 grain, 60 to 65 shots on regulation (30 FPE).

14.66 grain , 90 to 93 shots on regulation with an additional 20 to 30 off reg to 1000 to 1100psi (25FPE).

14.66 grain , 110 shots on regulation (20 FPE).


 
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Accomplished first three things on the list. Set regulator at about 2000 PSI (actually a touch less, but it's close enough), installed the B-Staley debouncer solution and installed the lighter valve spring. It cocks and fires, but haven't done any tuning. Should get some time to do some tuning in a couple days.

Thanks again for all the suggestions. First time I've "Modified" a rifle for efficiency.
 
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To get max shot per fill you need a hammer debounce. Something that stop the hammer from hitting the valve after it already strike the valve. Without it, the hammer bounce back and forth wasting air. There's many things you can do. Like add a HDD, hammer debounce, or lighter hammer, or stronger spring. Or ssg, spring system guide or whatever they call it. I forgot. But that's what I used. It's act like a sling shot. When you pull the trigger, it shoots the hammer to the valve. Without the SSG, I get about 30 shot at 30ft lb. With it I get about 55 shot at 30ft lb.
 
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