Originally Posted by CRAPGAME
I did this on a 98 cocker, last year I believe the valve chamber was smaller, I used red springs for both valve and IVG , was getting 30+ shots on 12 gram , set velocity for 275 high. Would hold at around that for 30+ good shots then drop off. Also under bored by one size( ran a freak .682, balls snug in .684- grafitti) hope this helps.
Thought '98 was the first year for the enlarged chamber. Either way, yes, the older 'cockers and Snipers with high pressure valves and low volume valve chambers were built to run on unregulated CO2 and require no modification from stock trim to run 12ies. My '93 Navarone Sniper3 is such an animal, even more so, perhaps, for being a Mini cut, and I recently set up a '95 Carter 'cocker the same way because I love the other one so much. Note that I typically use a 13ci bottle, so I don't have 12gram stats, but it's quite efficient.