Momentum is Mass * Velocity and Inertia which is a property of mass and the object of Newton’s second law of motion states that an object(mass) at rest tends to stay at rest and an object(mass) in motion tends to stay in motion, in a straight line unless acted upon by an outside force. Kinetic energy is equal to mass * velocity * velocity. It is inertia and momentum that fights the forces trying to slow the bullet down. Drag has a primary component in the creation of the sonic compression wave at the point of the bullet, and a secondary component at the base where there is a vacuum created by turbulence as the air flows over the base. Boat tail bullet creates a smoother transition and less area that is affected.
Momentum & Law of Inertia
It is momentum that drives the bullet into the target deeply to reach vital organs and the central nervous system. As the bullet contacts the target then begins a transfer of kinetic energy into the target creating the permanent and temporary wound channels, this is what kills. Momentum is what gets the bullet in deep of the target. Momentum is important. Look at the heavy dangerous game calibers. They drive relatively heavy bullets at or in excess of 400 grains (big mass) at moderate velocities. It is momentum and the high mass inertia that drives these projectiles through heavy muscle and thick bone to allow the transfers of huge amounts of kinetic energy. But even the lighter calibers used on deer, elk, black bear which are moving at much higher velocity still rely on inertia and momentum for penetration. It is bullet expansion and kinetic energy that contribute to the destruction. Inertia and momentum get you there.
Bullet Trajectory Physics
From the time the projectile leaves the barrel there two forces acting on the bullet, drag and gravity. How far the bullet goes depends on velocity. So long range numbers depend on velocity to cover the ground at long ranges before gravity drags the bullet to the ground. The better the bullet can fight drag the farther it will travel in the time allotted. At about 31 degrees from the horizontal will give you your maximum hold over for the longest range. High elevation of muzzle will shorten range. To much time is used up climbing higher and the bullet is subject to drag longer, shortening the range. Twenty-seven to thirty-one degrees gets you the farther than a higher elevation. On the moon with no atmospheric drag the maximum range would be achieved at 45 degrees muzzle angle.
Does the momentum/inertia contribute to the knock down or kill factors? Only so far as penetration goes. Kinetic energy transfer to the muscles, organs, central nervous system and bone is the killer. Momentum gets you in deep. The principles of inertia and momentum are tied together in physics relationship. Kinetic energy is the transfer of energy or the ability to do ‘work’ and a function of bullet expansion. Momentum/inertia is why heavier bullets will travel further given high enough velocity, the heavier more massive projectile tangles with the atmosphere and momentum drives it through the air. Light bullets lose the fight quicker, even given a higher muzzle velocity. 7.62 NATO has range advantages over the 5.56 NATO for this reason, but the smaller round was never designed for engagements much beyond 400 yards, that’s the whole idea of the assault rifle philosophy is that most engagement occur at 350 yards or less. Shooting Range Industries