n0tzl wrote:Was about to ask the same question since I'm trying to tune my .177 mrod for CO2 at the moment, since you haven't received a reply in nearly a year I'm not hopeful for much help but what the heck I'll give it a try.
Since my shooting at the moment is confined to a 10m makeshift range in the house figured I would give CO2 a try, the hand pump is great exercise and all but it does get old fast when I want to shoot a bunch, I'm still mulling over options (& finances) for an SCBA or SCUBA tank setup but don't really need a lot of power at the moment.
Had the gun tuned pretty good for a 2100psi air fill using CPH pellets, that tune gave me 550fps with both heavy & light Crosman Premiers with a CO2 fill so I started over with both hammer spring & stroke backed all the way out & the transfer port 4 turns out - that gave me 630fps with either pellet but increasing the spring tension made the velocity drop so I started shortening the stroke, have it 4 turns in now but think it will need a couple of more before the velocity falls, no matter what I've tried so far it won't go above 630fps, premier light, heavy, Gamo match, 2 other pellets and all about the same velocity - the premier lights have the best groups.
I'm getting 1" or so 10 shot groups at these settings but using air I can get 1/4" groups out of this gun with CPH at this range if I keep it above about 780fps, the CPL group about 1/2". I love the consistency of the CO2 velocity but wonder if I'm doing something wrong- is 630fps all the faster it will drive a 7.9gr pellet with CO2?
Has anybody else played with CO2 in a .177 mrod? Would love to see some comments about how it works and what settings you used.
Thanks, Dan
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