Gen 2 25 marauder tune

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drsquall

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Jul 22, 2022
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Hello,
I bought this gun years ago used and have just hunted with it and never tuned it. He said he power tuned it but it seems not so much with what I chrono graphed today.
2950 fill shooting jsb 25.4 exact kings
16 shot average of 761, SD 15, spread 52, about 34fpe.
Ending at 1800 psi ave of about 67psi per shot.

I don't know what these should be going velocity wise and the gun is accurate. Seems slow to me. It is all factory not aftermarket. Hammer spring was 5 revolutions cw out from all the way screwed in and hammer stroke was 4 turns out from all the way in. The valve was about 5 out from closed. I don't know what do to do. If you get it back to factory settings I would and see what is does. Do any of you guys know the factory settings or what to do. I just squirrel hunt with this so I would like at least 2 mags before having to fill back up. I'm new to this tuning so I need so guidance.

Thanks
Jon
 
It's slow. Skip worrying about factory settings, you transfer is where you want it. The stock is likely where is should be for power (further out = longer stroke/run at the striker pin so leave it at 1st. You should be able to hit roughly 40fpe.
Now your ES is awful which is where you will need to start playing with the relation between hammer spring and stroke length. Also you may well end up turning that transfer port screw in just a bit for a closer spread.
Sit down with it and have some fun. You should see a big improvement in all your number, unless perhaps some is actually broken.

John
 
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Make sure your breech oring is present, the stock ones rarely live a long life...

1684127586766.png

My guess is that is greatly effecting your FPS and spread...ask me how I know :rolleyes:
 
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Stubbers said:
Make sure your breech oring is present, the stock ones rarely live a long life...

View attachment 356627
My guess is that is greatly effecting your FPS and spread...ask me how I know :rolleyes:
Click to expand...
Searching for reasons my velocity is in the 600's and I can't tune it to get above 760's....my O ring is absent. Hoping the one thing will resolve my 2015 Marauder's velocity issue. Thank you
 
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