why is it.....

Originally posted by Dreadstone: Well, Knight pretty much sums it up quite succinctly.

A 5.56 can enter through your shoulder and exit through your lower back. For lack of a better term the round "tumbles" through the body as he said, "Shredding everything in between".

It's not necessarily the size of the round (.45 enthusiasts sit down. I see you), but the velocity. There's some serious kinetic energy that is transferred to you when you get shot

What really matters though is the force over time. As you say, It tumbles through your body... It may even pierce right through depending on the caliber. It takes time, and distance, to come to a stop, bleeding(heh) all that kinetic energy out all the little elastic lil fleshy bits it hits. The result is that a for most calibers on a live target, you're not going to get an appreciable knockback effect; You might stun a target capable of pain into physiological collapse where they just crumble to the ground- But not likely send them reeling the way you see in movies.

A hard target, though, like a tank or body armor... That's when you get a knockback effect. They stop a bullet HARD, preventing penetration. The result is all that kinetic energy transfers pretty directly into force against the target- And it does so near instantaneously (Measured in less than one thousandth of a second)...

For hard armor, You're talking the time it takes for a bullet traveling at, using 7.62x39 as an example, something like 2300 feet per second, to travel a distance from the moment of contact to full deformational impact. Against a hard target, that essentially means, the length of the bullet + the (typically negligible)depth of the dent at point of impact, which is what.. like 25mm not counting the casing for 7.62x39?

2300ft/s to travel 25mm is like 0.03ms, And in that split moment, all of that kinetic energy becomes heat, deforms the bullet- and imparts energy into the subject in a very violent manner- Which, yknow, for a guy wearing body armor, depending on the bullet absolutely could knock him on his ass or send him flying.

That time over distance matters a LOT, though. Bigger time and bigger distance = less force felt per unit time, shorter time and shorter distance = more force felt per unit time


So, If you shoot someone in body armor in one of their protective plates, Yeah, You're probably going to knock them on their ass or give them an appreciable nudge. But, shooting them in the squishy bits? Not so much. And anything big enough to give an appreciable nudge to a human in no armor is..honestly, likely to just punch clean through and kill em outright.