2260 with short crosman receiver atop a mini riser made from aluminum tube. Barrel is a 2200 soda straw
tensioned inside a titanium golf club shaft. Three screw mod to the trigger, bulk co2, SSP 250 rear cocking
striker assembly. Factory stock, reshaped, bedliner finish and stick on cheek piece. The idea was a weather
resistant light hunter for rainy days.
I've got a Cothran stainless receiver and gas tube waiting for me to get back to this one.
If I was you, I'd order a 1760 barrel from Crosman ( #1760-001 quoted $12.08 today ) which is a 24 inch .177 barrel, then cut and crown 1/2 inch at a time until you see a decrease in average velocity, then stop.
Make sure your bolt probe is long enough so that the pellet skirt completely clears the transfer port, but no longer. ( IMHO )
Any valve mod is likely to increase CO2 usage, but there are mods you can do to reduce it. ( at expense of velocity/power )
With your criteria of not increasing CO2 usage, I'm pretty sure there's not much else you can do.
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