Recently I've been investigating how armor damage works in Tarkov at present. I'm interested in this because it is pretty fundamental to understanding how effective an armor or a bullet will be in a situation with multiple hits. If you're not interested in reading the whole thing, I have a video here which will cover the same topic:
It also includes a link to a spreadsheet which is relevant to this.
Anyway, to begin with the important part is to clear up a misconception. Flesh damage has nothing to do with the armor damage, it is all down to the armor class, material, penetration and the bullet's armor damage percentage.
There's also a "catch up" feature where lower-pen rounds will get an additional bonus to higher tiers of armor, but it doesn't significantly change things, but does stop someone in a zabralo from being able to chest-tank a 60 round mag of 5.45 PS rounds without a scratch. Meanwhile, rounds which outmatch an armor will do slightly less damage, but as you're already penetrating it doesn't matter to you the shooter, aside from looting and repairing maybe.
One interesting observation of this is that 7.62PS is actually quite useable against the usual class 5 armors, the Gzhel and the Korund, which is thanks to the rather high armor damage percentage of this round. What happens is that it is behind say, 5.45BT for the first 4 shots, but upon the 5th they're both the same with a 94% chance to penetrate due to the damage done to the armor being higher per shot with PS than BT. So not bad at all for a trader 1 ammo.
I plan to make use of this with the penetration formula so that a more precise estimation and comparison of ammo types can be made than the usual NFAM chart that everyone uses.
Source: https://www.reddit.com/r/EscapefromTarkov/comments/z9av2h/how_armor_damage_works_a_guide/
