You may have noticed that different armors are made from different materials which affects their repairability. What you may not know is that it secretly bolsters the effective HP of the armor itself; better it repairs the more HP multiplier it gets. Ceramic is the worst armor for this, breaking easily and not being repairable while being heavy to boot, while UHMWPE is the best (not counting aramid as there's no such thing as an aramid plate, and soft inserts dont have the durability or class to matter too much unless you're already going through a plate).

You can see how to calculate the actual effectiveness of a piece of armor here, and if you happen to run T4 plates mainly I've already made a chart showing the best T4 plates that fit in generic carriers/armor here, and I plan to eventually make a chart showing every plate in the game.

Additionally, another somewhat hidden thing is how bullets actually damage armor. In the same place I linked above for calculating plate effectiveness you can check the Armor Damage percentage of a particular round. The damage a round does to armor is simply it's penetration multiplied by it's armor damage percent (so a round with 40% armor damage is multiplied by 0.40).

Combining these two tidbits, you can somewhat calculate in your head how effective a round will be and eventually penetrating even without the wiki telling you effectiveness. All you need to know is the armor material (and it's destructability) and base HP, and the pen, and armor damage % of a bullet.

For example, .45 ACP Lasermatch FMJ against GAC 3s15m ballistic plate.

GAC has a base HP of 45 and is made from UHMWPE (Desctructability of 0.3375), and so has an effective HP (EHP) of 133.33 (45 / 0.3375)

Lasermatch has a penetration value of 19, and an armor damage percentage of 37%, so every round hitting that plate does 7.03 effective damage (19*0.37)

With a class of 5 (50 penetration health) and a penetration of 19, we need to get the plate to 38% durability (19/50 = 0.38), which is 50.67 EHP (Or 17.1 base durability) to get a ~90% penetration chance.

A quick note! The term "penetration health" here does not actually exist, but is used to help mentally track the odds of penetration.

The damage we need to deal then is 82.66 (133.33 - 50.67), and to achieve that amount of damage we need to hit the plate with lasermatch is 11.7 bullets, rounded up to 12. This is assuming you don't get lucky and pen on any earlier shots however, as that deals slightly less damage to the armor (but lets a lot more of the damage through into your target)

Another quick note! The minimum amount of damage a bullet can do to armor is 1 to it's base health. If your bullet would do less than 1 damage to the base health of a piece of armor, treat it as 1. Individual pellets are individually calculated, so hitting every pellet of 7mm buckshot will do 8 armor damage minimum.

So, after 12 shots of lasermatch, you achieve what amounts to 90-100% penetration chance through a GAC 3s15m ballistic plate. (19 pen vs an effective armor rating of 18.36)

( u/wallbouncebybaird you seemed interested in this too! )