In deciding what gun to choose, especially for relatively new and young shooters, recoil is a factor. One way of comparing the recoil level of various calibers/gauges, loads, and guns, is by calculating the amount of recoil generated. This is only a limited evaluation of how the gun will actually behave in the shooter's hands. It does not consider burning rates of powder, possible effects of overbore (size of cartridge case relative to bore diameter), oversized bores in some target shotguns, fit of stock to shooter, geometry of gun relative to shooter, and other factors. Nevertheless, comparative recoil calculations are still a useful tool in choosing guns.<br><br>The calculations can be found in Hatcher's Notebook by Major General Julian S. Hatcher, 3rd Ed, 1966, Stackpole Books. Chapters 11-12, pp.253-300 discuss recoil. Especially see pp. 290-291 for a discussion of relevant formulae.<br><br>I have found very helpful the following simplified formula:<br><br> <br>R = { [ ( b V + 4600 P ) divided by 7000 ] quantity squared } all divided by 64.3 G<br><br><br>R = Recoil Energy expressed in foot pounds.<br><br>b = bullet weight in grains.<br><br>V = Velocity of bullet.<br><br>P = Powder weight in grains.<br><br>G = Gun weight in pounds.<br><br>For example, let's compute the recoil of a .30-06 rifle weighing a total of 8 lbs. (including scope, ammo, sling, etc.) shooting a 150 grain bullet at 2900 feet per second. A typical gunpowder may weigh 50 grains. Thus we know the following:<br><br>b = 150<br><br>V = 2900<br><br>P = 50<br><br>G = 8<br><br>Therefore,<br> <br>R = { [ ( 150 X 2900 ) + ( 4600 X 50 ) divided by 7000 ] <br><br> quantity squared } all divided by ( 64.3 X 8 ) .<br><br>Ergo, R = 17.5 foot pounds.<br><br>Note 64.3 = 2 X gravity<br><br>4600 = a physical constant<br><br>I apologize for the use of words rather than the conventional mathematical symbols, but that's a little outside of my usual area of work. I hope that the rarely seen the formula is as useful for others as it has been for me.<br><br>John<br>