well when I read pauls response I got a slightly different conclusion from barriers. and I will try to share:
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armored glass bar 3/5/2/2 integrity 6 this is more along the lines of your bullet proof glass, car winshields with the double layered safety glass or the like this is going to stop most light duty weapons and slow down or stop some high powered ones as well
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Just going with one of your examples, the armored glass.
A sniper rifle (AP5/BD4) will just punch through that glass as if it literally weren't there. The bullet is still AP5/BD4 if it hits a PC on the other side. But the integrity comes in to represent that just because a little bullet-sized hole was put through the glass, it doesn't mean the glass is automatically destroyed. Not unless all its integrity was destroyed by the attack that otherwise ignored the glass.
A typical assault rifle (AP4/BD4) will ALSO punch through the armored glass, but since it is 1 less than the barrier's rating, the bullet will be reduced to AP3/BD3) should it hit someone on the other side. No matter how many holes the sniper rifle already made, so long as the barrier's integrity is still at least 1.
