mikthestick

March 14, 2012, 06:28 PM

Found this old post leads me to believe few people who shoot understand recoil. Too many who shoot think they understand and don't.

1. Recoil is usually measured in ft/lbs 10ft/lbs would hurt you like if I dropped 1lb on your shoulder from a height of 10 feet.

FREE RECOIL is the energy the weapon develops if it were balanced on strings and allowed to jump back when the gun goes off. This energy is about 15ft/lbs for a WW2 rifle or 30 ft/lbs for a 12 gauge shotgun.

There are at least 2 formulas I know which calculate the recoil speed I'll use the one for modern powder. A US M1 weighs about 9lbs fires a 150gr bullet at 2800ft/sec with about 50gr of propellent.

(150 x2800) + (4700 x 50)

_______________________ = 10.4ft/sec

9 x 7000

Someone posted this formula and called it free recoil.

FREE RECOIL is half the mass times the velocity squared

0.5 x (9/32.16) x 10.4 x 10.4 = 15.1ft/lbs

Now the bit people don#t seem to get. If i take a piece of brick weighing a pound and drop it on your shoulder from 15 feet I expect you would need a trip to a hospital. So why can hunters shoot 20 rounds in a day and enjoy it?

The answer is they hold the rifle firmly against their shoulder. British WW2 veterans are known to have said of the 303 Enfield. "Hold it right or it'l break your shoulder. It is you weight behind the rifle which does not allow it to accelerate to its full potential. So if your body only allowed the rifle to go at 2ft/sec (my guess) you have to absorb only 0.9ft/lbs. If anyone is stupid enough to hold an M1 1/4" away from their shoulder with their arms relaxed and fire it. I would expect they will get a painful rude awakening.

1. Recoil is usually measured in ft/lbs 10ft/lbs would hurt you like if I dropped 1lb on your shoulder from a height of 10 feet.

FREE RECOIL is the energy the weapon develops if it were balanced on strings and allowed to jump back when the gun goes off. This energy is about 15ft/lbs for a WW2 rifle or 30 ft/lbs for a 12 gauge shotgun.

There are at least 2 formulas I know which calculate the recoil speed I'll use the one for modern powder. A US M1 weighs about 9lbs fires a 150gr bullet at 2800ft/sec with about 50gr of propellent.

(150 x2800) + (4700 x 50)

_______________________ = 10.4ft/sec

9 x 7000

Someone posted this formula and called it free recoil.

FREE RECOIL is half the mass times the velocity squared

0.5 x (9/32.16) x 10.4 x 10.4 = 15.1ft/lbs

Now the bit people don#t seem to get. If i take a piece of brick weighing a pound and drop it on your shoulder from 15 feet I expect you would need a trip to a hospital. So why can hunters shoot 20 rounds in a day and enjoy it?

The answer is they hold the rifle firmly against their shoulder. British WW2 veterans are known to have said of the 303 Enfield. "Hold it right or it'l break your shoulder. It is you weight behind the rifle which does not allow it to accelerate to its full potential. So if your body only allowed the rifle to go at 2ft/sec (my guess) you have to absorb only 0.9ft/lbs. If anyone is stupid enough to hold an M1 1/4" away from their shoulder with their arms relaxed and fire it. I would expect they will get a painful rude awakening.