I were to really make a match grade co2, would follow the lead of the last of real match co2 pistols.
Would use a "smallish" bulk fill tank becasue of weight issues. Would be dertachable/standard thread refillable. Gas would be in direct contact with the metal of the tank, so it would warm back up from self-cooling quickly (10 meter shooting is normally in an eviormentally controled space).
Would be "bare barrled" so the exiting co2 gas wouldn't have a 2nd pass at cooling the barrel. Besides, a 4-5 fpe .177 really isn't all that loud and the less "crap" hung on the barrel the more natural the vibration cycle.
Keeping to match speeds, woud use a lite striker, short stiff spring, and a short stroke. Not only would that provide the match type speeds, but likely produce less vibration/weight shift inside the pistol during the shot.
Anyway....the best of my 12gr. guns is an Alfa Proj, bought used, and shortly after my wife saw it/hefted it, she "claimed it"...so it's hers now. Not really a full match rifle (it's too light and the adjustments of the sights/ stock aren't "fine" enough)...but close enough.
(No blame to her...there is something about this little slim rifle that does to women...every time I've left it out, a woman has always been the first to ask about it...why? Not really sure.)
Odd 12gr. The 12gr. cartridges fits into the pistol grip upside down...it's pierced by the bottom end cap...co2 gas has to run into a very small pressurized tube, up though a tiny opeing, and into the action.
At frist, I'd have thought that the upside down piercing of the 12gr. would promoted liquid co2 injection. But the convoluted path it takes pertty much preculdes that ever happening .
"They" (the makers) do provide a bulk fill option....but I've only used it once or twice.
With one 12gr., in warm weather, have managed 85 shots at 4.2 foot pounds (ok...that's an average of several pellet weights in this test).
The long rectangular barrel cover masks the shorter barrel. MAY not have been dseigned as such, but it makes a prtty goof (large volume)single shamber shroud.
Whic still works out to (85X 4.2) 357 foot pouds per 12gre. (which can be anything from 10.9-11.9 grams rather than 12).
LESS accurate, is an old Crosman Clallenger 2000. Has been much adjusted.made over/poilished. trigger tuned, but still runs on the original parts).
WAY less refined than the Alfa (but as my wife took the Alfa, it's the "best" single 12gr. shooter I have that I can call "mine"). Will do 75 shots (on a single 12gr.) at 4.5 foot pounds.,,sometimes gets up into the high 80's..but this is more typical.
So that's 4.5X75...which is 338 foot pounds per 12gr.
Before you "fuss at me" about the groups...both shot with the sights you see in the picture (although under bright daylight)...so "match" sights, old-guy eyes.
They only "trick" to shooting a single 12gr./ non-tube filling co2 has been to GO SLOW...has to reach some kind of equlibrium between the pace of shooting (which is the the self cooling feature of co2's gas-to-liquid conversion) and the exernal heating to ambinat temperature.
I do know more than that shot count is possible.
With enough fiddling around, time, effort, know that "sporters" can reach or exceed that shot count/energy level per 12gr.
Worked on a sinple Fusion. Striker weight.striker spring tesnion, transfer port were all "fiddled" with. While I do hate the variable nature of the accuracy, it does give a pretty good shot count (ofr 2X12gr.)
But the 760 foot pounds for TWO 12gr. works out to 380 foot pouds per ONE 12gr....which qouls be rate if I could really count of the rifle not to shoot like crap every 2nd or 3rd time I took it out).
Lastly is a 5mm QB conversion, also running on 12gr. (2X 12gr.). Not as "weak" as the others, looking for more like 12 foot pounds, and it might do better in warmer weather.
Only 52 "good" shots, but at 612 fps/ 11.8 fpe per shot, that works out to 320 foot pounds per 12gr.
So I really do not think that, at least between 4 and 12 foot pounds of energy, that 300 foot pounds per 12gr. is not an unreasonable goal to ask of a 12gr. shooting pistol or rifle. Can certainly get more shots (at less energy) or more energy (at fewer shots).
But to me, it's the goal-line...300fpe for one 12gr...600fpe for two. Can boost power up if you care to, but it you manage 20 foot pounds per shot, I'd want 15 shots per 12gr.