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Old 4th October 2013, 01:25 PM
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rich rich is offline
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Join Date: Nov 2008
Location: Shebbear, N Devon
Posts: 1,643

Re the springer v PCP comparison; the ways they deliver the energy to the pellet are the inverse of each other.

The instantaneous pressure in a springer, at the moment the pellet "lets go" of its hold in the breech, can easily be several hundred bar. The compression of the air is almost adiabatic; there isn't time for any heat to be lost to the surrounding metalwork and instead it goes into increasing the pressure more than the straight compression ratio would indicate.

As soon as the pellet moves, even just one transfer port length along the barrel, that pressure is down to about half from that peak. It continues to drop as the advancing pellet leaves a bigger and bigger void space behind it.

OTOH the precharged rifle continues to deliver air - and more air - maybe four times as much as a springer - for the entire travel along the barrel. Many PCPs still have the firing valve open when the pellet has left the muzzle. The Daystate Airwolf with its solenoid system is the major exception. This extra air is why unsilenced PCPs are noisier than springers, in the main.

Years ago I experimented with a 20fpe HW80 firing pellets into a butt of water; almost every brand of pellet had the skirt blown out from a taper to a cylinder by the initial blast of air. The resulting pellet was more bullet shaped than waisted.
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