I thought you might be interested in what I have discovered so far:
The muzzle velocity of the escaping gas from a rifle is around 4,000 fps, plus or minus about 10%. This has been determined by actually measuring a range of different cartridges.
The cartridge recoil impulse is basically concerned with momentum (mass times velocity), not energy (mass times velocity squared). However, the perceived gun recoil is concerned with energy.
The same cartridge fired from a light gun and a heavy gun will deliver the same momentum to each, but as the light gun will be recoiling faster it develops more energy, and that's what the shooter notices as increased recoil.
Alternatively, if two rifles of the same weight fire two different cartridges, one generating twice the momentum of the other, the rifle firing the more powerful cartridge will travel backwards twice as fast, which translates as developing four times as much recoil energy. This explains why the 7.62x51 cartridge develops only double the recoil impulse of the 5.56x45, but the perceived recoil is four times greater.
Tony Williams: Military gun and ammunition [URL=http://www.quarry.nildram.co.uk]website[/URL] and Discussion [URL=http://forums.delphiforums.com/autogun/messages/]forum[/URL]