First off, I could swear I read something about this but I couldn't find it when I looked again- so here I post.
I am using a Tactical Vest that I made, which gives 9 base Mechanical Damage Threshold, so it should give 27 total Threshold vs. any kind of bullets.
But I'm going up against Sentry Bots and it is only using the base 9 Mech DT.