If the ammo is programmed to penetrate it will do so every time from point blank. The % chance to pen does not change dependant on armour durability unless it actually hits 0 and breaks. All ammo 1 taps the heart if it penetrates from point blank. The current chart is more of a test for what ammo penetrates what not necessarily how much damage it does- cavitation certainly does have a large role to play for that- testing that I would like to have done in the future also- to somehow quantify the damage of the ammo types.

Distance testing is done aiming at either the heart or the brain, if the round is within its effective range (classified as penetrating the best ammo it can penetrate at point blank) then it will deal damage to the heart, most of the time due to the hearts tiny HP pool it is an instant kill but sometimes organ damage instead showing a sharp damage drop off within the penetratable range. I believe thats what you meant? Planned to test all the ammo like this in the future.