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Ralgha · August 13, 2011, 10:32 AM

Recoil is impulse, not force. The flaw in your reasoning is that the force applied in the .40 is, in fact, greater than the force applied in the .45.

The reason you all come up with the two having identical force is that you're discounting time. They would only have identical force if the bullet was accelerated instantly, which is what is assumed in the equations you are using.

Both calibers go at the same velocity (virtually), the .45 is accelerated by a lesser force over longer time (lower impulse) and the .40 is accelerated by higher force over shorter time (higher impulse). The equation for force that you need to use is F = (change in momentum) / (change in time). Then find the impulse by taking the integral of that force over time.

August 13, 2011, 10:32 AM	#16
Ralgha Senior Member Join Date: February 5, 2011 Location: Oregon Posts: 123	Recoil is impulse, not force. The flaw in your reasoning is that the force applied in the .40 is, in fact, greater than the force applied in the .45. The reason you all come up with the two having identical force is that you're discounting time. They would only have identical force if the bullet was accelerated instantly, which is what is assumed in the equations you are using. Both calibers go at the same velocity (virtually), the .45 is accelerated by a lesser force over longer time (lower impulse) and the .40 is accelerated by higher force over shorter time (higher impulse). The equation for force that you need to use is F = (change in momentum) / (change in time). Then find the impulse by taking the integral of that force over time.