1. The round, at the range you fired it
Damage and penetration are both curves, not constants, and each round ships its own. Past point blank the curve supplies the damage outright rather than scaling the round’s headline figure — so a round’s printed damage stops mattering the moment you step back from the muzzle.
Most rifle profiles are flat out to 70–200 m, so the curve rarely bites indoors. The exception is 12 gauge buckshot, flat only to about 15 m.
2. The gun contributes exactly one number
Of the six figures the gunsmith screen shows, only firing power reaches this model at all (fire rate turns shots into seconds, but does not change any of them). Ergonomics, ADS speed, spread and both recoil axes reach nothing here.
factor = 0.9 + 0.2 × firing power
The percentage on the bench is that factor, times 100: a gun reading 105% is a factor of 1.05. Which is why the inspector asks for the percentage — it is the number you can actually see in game.
3. Where it landed
Every bone carries one multiplier, and the game applies it before any armour is consulted. There is no separate, lower multiplier for a limb already at zero HP — a destroyed leg takes exactly what an intact one does.
Hands and feet have no entry of their own; a recorded foot hit behaves as a calf hit. Only the head and the upper chest are fatal at zero — everything else is a crippled limb, though the damage still comes out of one shared 440 HP body.
4. The plate is worth less than its badge
Durability does not merely run out — it scales the armour class itself. The game reads a curve at how much durability is missing, and multiplies the zone’s class by the result.
effective class = zone class × curve(1 − durability ÷ max durability)
A class 5 vest at 40% durability is not a class 5 vest. In a recorded in-game sequence an IMTV walked from 5.0 down to 3.5 over sixteen rifle hits, and the round that had been bouncing all along went through on the sixteenth without anything about the round changing.
Zone class, not the badge. A piece rates each body part separately and the headline number on the item card is a display field. A 6B45 badged class 5 carries class 5 on the chest and class 4 on the pelvis — a full class of difference, on the same vest, decided by where you aim.
5. The gap, and the roll
Armour class and penetration are the same axis, so the game simply subtracts them. That difference — not a ratio — is what both armour curves are read on.
gap = effective class − penetration
The gap goes into the penetration chance curve, and the game draws a number: it goes through when the chance is at least the roll. A gap of +1 or worse is a hard zero on every shipped curve; a gap near 0 is around 85%; and a plate at zero durability is bypassed outright, with no roll at all.
6. What survives, either way
Through: the same gap is read on a second curve, clamped at −2. Beating the armour by a full class already gives full damage, and there is no reward past that.
Stopped: two multipliers, both small — the round’s own blunt scale, and the blunt scale of the zone it hit. On a class 6 vest a 5.56 FMJ comes out at about 2 HP a shot. That is the useful discriminator in game: on most vests a bounce is 1–7 damage and a penetration is 18–60, an order of magnitude apart, so you never need a precise reading to tell which happened.
7. The plate’s own bill
The armour loses durability on every hit it covers, stopped or not, and a penetrating hit costs it more. It is billed from the same base figure the body is — body-part multiplier included, firing power counted once.
Which is the one free discriminator in game: full damage and zero durability lost happens only when the gear did not cover the hit at all. Every other way of taking a big hit still spends durability.