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Easy Marauder CO2 settings

June 15 2012 at 10:21 PM
Jobo  (Login JRFArizona)
YF12

I just wanted to share the settings I use for CO2 on my Marauder.

My Marauder was originally a stock 0.177. The action is still stock (no HDD and still original hammer spring), but I bought the (manufacturer) 0.22 parts for it, so I've tried it both as 0.177 and 0.22. The ambient temperature for my tests was the low 80s F.

For 0.177 to get the maximum muzzle velocity for 8.4gr JSBs (with the least hammer force), I use
- maximum valve (4 or more turns counter clockwise [ccw] from full close)
- minimum spring pre-tension (0 turns clockwise from full ccw)
- minimum hammer throw (12 turns clockwise from full ccw--12 is the maximum usable according to the manual)

I got about 731 to 739 fps for the 8.4gr JSBs with the above settings (about 10 fpe). Changing the hammer and spring settings didn't change the velocity, just the noise (and vibration). Turning the valve in clockwise decreased the velocity.

For 0.22 to get the maximum muzzle velocity for 15.9 JSBs, I use similar settings to get about 633 to 640 fps (about 14.5 fpe). Everything is the same except for
- short (but not minimal) hammer throw (10 turns clockwise from full ccw)

I fiddled with the spring pre-tension also, but after several tries, found the hammer throw adjustment to be the easiest (and I think most appropriate). If the temperature and pressure were higher, then maybe adjusting the spring pre-tension would be more appropriate.

I haven't done any shot counting in 0.22, but in 0.177 I got about 27 to 30 fpe per gram of CO2 used up (so at 10 fpe, I got about 3 shots per gram, but at 7 fpe, I got about 4). I generally got minimal extreme spread (less than 10 fps) in the first 12 to 13 grams from full, after which the velocities went down bringing the ES to about 25 fps at about 20 grams used up. Unfortunately the fill weight varied from filling to filling. In these scenarios the pressure gauge moved very little from full to the beginning of velocity drop off (less than 100 psi difference).


 
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