Alpha damage
The damage a single penetrating shell deals, before the plus or minus 25 percent the game rolls on every shot.
Also known as alpha, damage per shot.
Alpha is the headline number on a gun. A quoted 390 means the shell averages 390 damage on a penetrating hit, with each individual shot rolled anywhere between 293 and 488.
High alpha is worth more than the average suggests, because damage arrives in one piece. A single 750 shot forces an opponent to retreat and repair where three 250 shots give them time to answer between each one, and it is the entire argument for slow, heavy-hitting guns.
It only describes a full penetration. A hit that fails to penetrate deals nothing, and a high explosive shell that does not penetrate deals a reduced splash amount instead.