PDWs...and other small arms.

[stanc]

Stan: You probably won't penetrate it with any single shot from any small arms. Multiple shots and who knows but from guys I know who did get shot in chest plates, the impact knocked them down pretty hard.

Yeah, that can sure be seen in these videos. One soldier described it as like being hit with a sledgehammer.

[video=youtube;JxeP9SjJt68]https://www.youtube.com/watch?v=JxeP9SjJt68[/video]
https://www.youtube.com/watch?v=JxeP9SjJt68

[video=youtube;tMMSA3opBk4]https://www.youtube.com/watch?v=tMMSA3opBk4[/video]
https://www.youtube.com/watch?v=tMMSA3opBk4

May be able to cleave it with your tomahawk or perhaps stab through with your knife.

Why a PDW anyway if the best way to prevent fratricide (when being over run) is to discard your firearm and use 'cold steel'?

LOL. Now you're just being mean.

But seriously, if it should be deemed necessary for small arms to be able to defeat modern hard armor, it looks to me like the only way to possibly achieve that is to go the route that the Russians started down three decades ago: Intermediate caliber, ultra-high velocity.

Developed for machine gun and sniper rifle, the 6x49 Unified (below, center) had a 77-gr steel-core bullet @ nearly 3800 fps.