What about the effect of the gas laws: Charles and Boyles? It seems to
me that the force accelerating the projectile is caused by the pressure of the
gases produce during the explosive combustion of the powder and detonator. As
the projectile (piston) moves down the barrel (cylinder), the volume of the
gases increases, thus pressure (and force) drops. Simultaneously, as the hot
gas expands down the cooler barrel, the temperature drops, again lowering the
pressure. It should not take long before the pressure reduces enough so that
there could be no more acceleration.
Does anyone know some typical values or ranges of the amount gas
produced and the initial temperatures?
Would a hot barrel keep the gas hotter thus increasing muzzle velocity?
.... or does the expansion of the barrel allow more gas to "leak" thus reducing
muzzle velocity?