Plenum-size (Artemis/SPA/SMK P22), what does it say us?

[rumbleUU]

Just measured the total plenum size after the regulator all the way to the where the poppet seals inside the valve and got:
6,2+1,1+0,6+5,7  -0,38-0,2-0,2  = 12,8 CC, this is a rough calculation give or take 10%

What can we say about this size plenum behind a .22 pellet and lets say 150 bar regpressure, is the plenum size OK?, to small?
what FPE is to be expected with resonable efficency? (imagane the breathing is good all the way from poppet/stem to the pellet, no restriction)

I think the barrel is almost 21" length

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The strange thing is, a FX Crown has like 25-30cc plenum from reading, how can this M22 wich is a powerfull PCP only have 12cc? I dont think my calculation are wrong

[rsterne]

I would say that the plenum is smaller than I would use for a "high powered" .22 cal.... but you can make up for that by increasing the regulator setpoint.... Generally, that approach hurts the efficiency, and the shot count, however....

Bob