I did some calculations, comparing thorax hits with no body armor to thorax hits with PACA.
The results are as follows: Out of 137 different types of ammo, the PACA does not add a single more shot to survive for 51 of them. That is 37% of all ammo types in the game. Furthermore, for 29 of the remaining ammo types, the number of average shots survived more than without any armor was one shot or less. That is 21%.
So for 56% of all ammo types, the PACA merely adds one extra body shot. For the price of the armor, that is not good performance. To put this in data: The median increase of survivable shots for the PACA ammo was 1.0.
However, there were some kinds of ammo, where the PACA did offer significant protection: 20x70mm and 9x18mm.
For 20x70mm, the PACA increased the amount of hits taken from 1 to 3 for most types of ammo. Paired with the slow fire rate of the TOZ, this greatly increases survivability.
For 9x18mm, the average hits survived with no armor is 2, regardless of the specific ammo used. The median of survived hits with PACA armor is 7.8 instead of 2.0, with the lowest being 2.1 for PPM ammo, and the highest being 10.0 for SP8 and 9 P ammo respectively.
While this sounds amazing in theory, many 9x18 weapons are also fully automatic with a high firerate, such as the PP-9* variants and the AP* pistols.
For the majority of cartridges available in the game, PACA offers either no or only extremely limited protection. This is true for many of the commonly used cartridges by entry-level players (available by LL1 traders or commonly found):
- 5.56x45mm M856 (+1 round)
- 5.45x39 BP (+0.1 round)
- 7.62x39 PS (+0 rounds)
- 9x19mm Pst (+1 round)
- 12x70 7mm (+1 round)
The only time the PACA adds a significant factor for survivability is the TOZ-106 shotgun, as well as the Makarov pistol, which are somewhat common on Scavs. For all other guns, the PACA performs very poorly.
So if your explicit goal is to hunt Scavs and you wish to remain lightweight or on a budget, then PACA armor can be useful. In all other situations, it is a waste of money and body weight.
Just for comparison, the 6B13 assault armor, which can be found somewhat regularly in raid or bought from Ragman LL2, has a median increase in survivable shots of 7.5 instead of 1.0.