Your understanding is completely and totally wrong. (no insult intended), armor worked to both lessen the impact of injuries (turning a potentially crippling injury into a minor inconvenience) and to completely negate strikes entirely. A good suit of platemail renders one almost impervious to sword strikes and highly resistant to arrows and even early firearms. It required either the heft of a polearm or heavy mace\axe to cause serious injury to somone in full plate, or the precision of a dagger to strike at the weak points.
You forgot to mention certain specialty weapons developed specifically for piercing armour. Or crossbows with especially made bolts or 150lb draw long bows with similarly armour piercing arrows.
You are right, though. I should have at least said.
Armour, in most cases, wasn't really intended to prevent injury. Although, armour could stop a glancing blow or seriously negate some types of weapon strikes it was mostly to give the wearer a better chance of preventing death. Shields and foot work were used to prevent injury more than anything as I understand it.
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You do realize that .22 and .223 are virtually the same caliber right? It's a matter of the size of the charge behind the bullet, .223 typically being a very large rifle cartridge.
I started writing this before Footkerchief responded so I am going to leave it. They are essentially the same caliber, yes. However, they are no where near the same bullet or cartridge casing(shell) and the distinction is important because people tend to use caliber(diameter of gun barrel bore) in place of bullet and shell. The .223 is ~10% to ~90% more massive than a .22lr depending on the specific manufacturer/model. Additionally, the .223 is much more streamlined than the .22 and the muzzle velocity is close to 150% above that of a standard .22lr.
For the record, Type I armour should protect against a .22lr.
Type III armour should protect against ball variety but not AP variety
7.62x51 NATO.
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I heard it described that heavy armor can have a problem with arrows, namely that lighter armor allows the bolt to pass right through, while heavier armor leaves the bolt in place, moving around and reopening the wound.
I am not sure what is better, having an arrow completely negate your armour or have it lodge in the wound and the armour. I suppose in some specific circumstances the arrow passing freely through the armour might be better. But if heavy armour is the difference between critical damage to a broken rib that doesn't impale the liver vs. one that does I think heavy armour would be superior despite the tendency to open the wound a bit in the interim.