Using ball ammo as it's called, it's not unusual to need 200 shots to kill 15-20 people. It's designed not to expand, just pass through and incapacitate. Thsi goes way back to earliest Geneva Conventions.
War is a financial endeavor. Killing somebody only costs a bullet, or 50, and is frowned upon. Wounding somebody and causing all the logistcs of saving them on the field, and then sending $$$$$ for recovery and rehab is the goal and has been for decades.
The fable of a 223 hitting somebody in the hand and going out his heel is alive today when describing a hit on an upright person. Take the same person and put him in the prone position and yes, that non-expanding round will go in one end and out the other.
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