Can anyone point me to a reference which shows detailed calculations for the recoil impulse generated by small arms cartridges? My understanding of the calculation is that it consists of: bullet weight x muzzle velocity + propellant weight x muzzle velocity (around 4,000 fps). However, if this is applied to the 5.56x45 and 7.62x51, it results in the 7.62mm having almost exactly double the recoil impulse of the 5.56mm, whereas I keep reading that the difference is much bigger than that.

Thanks for any help.

Tony Williams: Military gun and ammunition website and Discussion forum

I always use the following website: [URL]http://www.chuckhawks.com/recoil_table.htm[/URL]
Dan

I'm not sure you have the complete formula.  I've used this one by Hodgdon with good results.

Hodgdon's formula is:

Bw Mv + 4700 Pw 2(i.e. squared)

divided by

64.348 Gw

Gw is the weight of the gun in pounds
Bw is weight of the ejecta in pounds
Pw is powder weight in pounds
Mv is muzzle velocity in fps

The calculation is on Page 38 of Hodgdon's Basic Reloader Manual.

Many thanks!

Tony

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]