Handloader:
Free recoil is the right thing to look at when comparing how a gun "feels" in your hand. My NRA Firearms Fact Book (Third Edition) has a very good explanation of the factors in calculating free recoil. Momentum of the gun = momentum of the projectile + momentum of the powder charge.
There was a NOVA program on PBS, Einstein's Big Idea, in October that also covered the subject. Newton's statements of the three laws of motion introduced impulse (Force x Time) and momentum (Mass x Velocity), but the concept of kinetic energy as ( 1/2xMassxVelocityxVelocity) wasn't formally stated until the 20th century. Newton's laws of motion treated conservation of momentum, not kinetic energy.
In any event, the NRA treatment states that "The recoil impulse depends essentially upon the ammunition, and is independent of the weight of the gun." Also, "The free recoil velocity can make it unpleasant to shoot, even if the recoil impulse is not excessive."
It's a good thing the kinetic energy of the projectile is not what you feel - that 440 grain .500 S&W projectile has a kinetic energy at the muzzle of 2577 ft-lb. Assuming you're a big guy holding the gun 18 inches in front of your body, you would have to be able to hold 1700 pounds!!
Sorry for the Physics 101 lecture, but a lot of people seem to get off on the wrong trail.
Steve S.
