I plan to make a gun that shoots broken glass. Obviously, since it's glass, it shouldn't be useful against armored targets, but very painful to unarmored ones.

I want to know 2 things:
1. How to tweak the gun and its glass shards so that it only really affects unarmored targets, and
2. How to make it so that when it strikes a harder target, it shatters.

Thanks in advance.

If you use mopixels you can just adjust sharpness untill it doesn't affect armor but devestates exposed flesh.