Originally Posted by Conor
Was it because they were tight or heavy or possibly both that resulted in the high energy
So is it fact that a spring gun set up to 11.9ft/lb using 7.9grn sized pellets will produce a higher muzzle energy than if a 10.6grn pellet sized to the same diameter was shot in the same gun ??
I think it was because they were tight ... not the heads tight in the barrel ... but the tails sitting tight in the curved entrance to the breech ... so pressure built up behind them before they started moving and the pressure behind them started to drop. In other springers that I have ... plenty ... the lighter pellets give the best energy and the heavy ones the least energy. It's commonly known that this is usually the case. So I'm presuming that the heavy Barracudas in that Vulcan were so efficient because they had a tight fit in the breech. Maybe as Rich says it's because they sat further back and so the pressure would build up behind them more because the swept volume was being forced into a smaller space. To be fair to Cardew he did say that the most efficient entrance to the breech is a curved one and not a countersunk one.
NORMALLY ... if you set up a spring gun with a 7.9gr decent pellet at 11.9fp and then try a 10.6gr pellet it will probably be doing about 1fp less ( so closer to 11fp ). and NORMALLY ... if you set up a pcp with a 7.9gr pellet doing 11.9fp and then use a 10.6gr pellet it will probably be doing closer to 13fp.