Russia claims their new future body armour will stop a .50 cal

[SnowFella]

Here's a good one for temporary vs permanent cavity, temporary is caused by the shockwave and permanent by the bullet mushrooming or fragmenting.

You Tube

Note the first test, 16 inches of ballistic gel and there's no permanent cavity to speak of. First few inches is virtually an icepick hole, fair enough a .50 icepick hole but nothing earthshattering.