Re: When does recoil occur???
While “recoil” is certainly related to Newton’s third law of motion that for every action there is an equal and opposite reaction, recoil is actually the phenomena which occurs when the expanding gas column which propels a projectile inside a cylinder suddenly clears the end of the cylinder and the gas rapidly expands, and it is this force that once it has transferred to the barrel causing it to move in the opposite direction which we call “recoil.” Therefore, it may be observed that a shorter barrel produces a far greater recoil than a does a longer barrel because the shorter barrel has less internal volume for the gas to expand and is thus under a greater pressure when it vents than does a longer barrel which because of its greater volume contains a lower pressure when it is vented (i.e. when the projectile clears the muzzle). Until this point, the internal expansion of the gas does not translate into any measureable motion within the barrel, and if any part of the explosive chain could be felt, depending on the relative mass of the barrel it would perhaps be the movement of the projectile's mass within the barrel affecting the equilibrium or balance of the barrel, but not causing or contributing to any kind of recoil force, least not until the projectile escapes from the cylinder. So it is the internal gas pressure at the moment it escapes and expands from the barrel rather than the mass of the projectile that equates to the force of the recoil. The weight (i.e. mass times gravity) of the projectile is but a small portion of the total recoil force. Theoretically, if a barrel was long enough to compensate for the full volume of the gas pressure, the forward motion of the projectile would literally stop and there would be no recoil.
First Cousin (7 times removed) to Brigadier General Stand Watie (1806-1871), CSA
1st Cherokee Mounted Rifles | Principal Chief of the Cherokee Nation 1862-66
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