Well, like I said. That was just an extra part that you might possibly consider, given the fact that yes, it was a grenade launcher, but it shot smoke or teargas and couldn't be used as a weapon in itself.
But alright. Just take that part off. How about the main idea?
Dunno.
I might post some values for the vests, later. How much protection/etc.
[Edit]
The vests seem to need more work than expected.
Anyways, I'll just make it very basic for now. Here some stuff I just came up with...
Light vest:Damage under 10: 80% protection
Damage 11 - 18 (9mm): 60% protection
Damage 19 (5.7mm) - 20 (.45 ACP): 40% protection
Medium vest:Damage under 18: 70% protection
Damage 18 - 20 (.45 ACP): 60% protection
Damage 21 - 23 (5.56mm): 30% protection
Heavy vest:Damage under 23: 80% protection
Damage 23 (5.56mm) - 25 (7.62mm): 60% protection
Damage 26 - 30: 25% protection