Velocity vs Man Power?

[steve4102]

We all know about Newton and his Equal Action and Opposite Reaction rule, right.

I just read a comment that a human being can reveres Newton's law and transfer more energy to the Forward motion (Muzzle Velocity) to a bullet by holding the rifle closer and tighter to the shoulder.

Is this a Physical possibility? I always though that "Equal and Opposite" was a Law of Physics and we mere mortals cannot change these things with muscles and the like.

[Bart B.]

The more resistance there is to rifle recoil during the time the bullet's going through the barrel, the faster bullets will leave the muzzle relative to the ground.

I shot 20 rounds one evening from a bench alternating the stock's hold against my shoulder from light to heavy; weak to strong, or whatever you like. Average muzzle velocity spread shooting M118 match ammo in a 12 pound Win. 70 match rifle was a bit over 40 fps. Shot that same rifle and ammo slung up in prone as well as standing without a sling. Bullets left faster from prone by about 20 fps.

Think about what happens if a cartridge is fired from a SAAMI spec test barrel clamped horizontally in a steel block that's bolted to a cubic yard of concrete shooting rounds with a 2000 fps muzzle velocity; that barrel doesn't move back in recoil at all when rounds are fired. If that barrel and steel block was moving backwards 2000 fps on a track, the bullets would fall straight down to the ground from the muzzle when they left it; zero horizontal velocity over the ground.

Consider the nose gunner in a 200 mph B17 Flying Fortress shooting his 50 caliber BMG straight ahead; those bullets are leaving almost 300 fps faster over ground than the 50's bolted onto Jeeps. The tail gunner's twin 50's bullets fired straight back leave almost 300 fps slower relative to earth than the ones on the ground. Relative to each BMG's barrel, muzzle velocity's the same at about 2900 fps.

Newton's law is not reversed in either situation.

[Unclenick]

Steve,

What is equal and opposite is accelerating force resulting in equal and opposite momentum in the gun at one end and the ejecta at the other. For the latter, you have momentum of the bullet at the muzzle, plus momentum of the powder mass accelerated to become the muzzle blast at an even higher velocity (rocket effect). A solid anchor makes the gun react against the whole earth, whereas when it is held loosely it reacts mostly against its own mass (free recoiling) during the time the bullet is in the barrel. The same force will accelerate the much smaller mass of the rifle a lot more than it will the whole earth, so the same momentum in both represents a pretty big disparity in velocity.

[Nick_C_S]

Absolutely. Absolutely.

I've loaded weak semi-auto rounds that will FTE if I hold the gun loosely, and cycle fine if I grip it tight.