[miclo18d]

It has even changed since I retired but I'll give you some info on ballistic protection.

(Picture 1)
I enlisted in 1988 and we wore steel pots in basic training. When I hit airborne school, we were issued "K-pots", Kevlar helmets and had those for about 12-13 years. During Just Cause, one of the guys in my company was shot with a pistols at point blank. The bullet went in between his head and the inside of the helmet, circled at least one time, and exited, basically skimming the inside of the helmet. I went to "SOT light" in 93 and was shown 5.56 and 9mm holes through and through to the k-pots. Asked my self why the heck are we wearing these things?

(Picture 2)
At some point after 9-11 we were issued the MICH helmet. A cut dow'n light weight K-pot. Nothing to report about the MICH other than it was very light and much more comfortable than the K-pot. Then before my 2nd deployment to A-Stan in 2006, we were issued the ACH. It looked and weighed the same as the MICH. I saw 2 separate instances of perpendicular head shots where the bullet was stopped with the ACH. The soldiers were effed up bad (TBI) but the bullet was stopped completely.

(Picture 3 sort of)
Bump helmets were used in the days of the steel pots and k-pots probably because they didn't stop bullets and the guys that wore them needed speed vs protection. Most used skateboard/hockey helmets. Used to prevent getting bumped in the head by say a little bird blade I.e. Just Cause. Now ballistic protection is getting lighter and stronger that they are incorporating it into bump helmets. Not to mention that they have cut down the ACH over the ears to lighten and improve access for electronic ear protection.

ETA: after seeing the 2 head shots stopped, I wore my ACH everywhere!