Quote Originally Posted by Shed tuner View Post
nope, you've misunderstood... although your definition of peak pressure in a conventional firing cycle is fine; probably my crap explanation to blame ! Nothing to do with pellet fit. If the pistons don't meet correctly in the middle, the pressure that may make reduces exponentially.
In that case I am still a bit puzzled. If the springs are of equal strength and length then the pistons will always eventually come to equilibrium in the centre of the cylinder, with all the air expelled. You can't get a situation where one piston has traveled past the exit hole and the other hasn't reached it, and there is a volume of compressed air permanently trapped in the cylinder. (Though you could if one spring was longer and stronger than the other).

If there is a mismatch with the timing I imagine there would a transfer of energy from one spring to the other from the building-up air pressure as they travel towards each other, in a kind of shuffling process, until they finally end up in contact at the centre with all the air expelled.

But you could be right. I imagine that technically this is a very complicated process (and very interesting) and the only way to sort it out would be to make an example of the pistol and road test it. As a result I have moved it up my priority list of projects!