Overmatch

The rule that a shell with a caliber at least three times a plate's thickness cannot ricochet off it, no matter the angle.

Also known as 3 caliber rule, overmatching.

Overmatch is why large-caliber guns ignore armor that stops smaller ones. A 122 millimetre shell overmatches any plate up to about 40 millimetres, so a sloped 30 millimetre roof or a thin angled side is defeated as if it were flat.

It has two consequences: the ricochet check is skipped entirely, and normalization is amplified, so the effective thickness collapses toward the nominal value.

This is what makes the difference between a 105 and a 122 millimetre gun larger than their penetration figures suggest, and why the thickness of a light tank's upper plate is chosen so carefully against the calibers it will meet.

Related terms

RicochetA shell deflecting off a plate without any penetration check, which happens beyond 70 degrees for most shells and 85 for HEAT.CaliberThe diameter of a gun's shell in millimetres, which sets what armor it can overmatch as well as roughly how hard it hits.NormalizationThe few degrees a shell turns toward the perpendicular on impact, reducing the effective armor it has to cross.Effective armorThe thickness a shell actually has to defeat once the angle of the plate is accounted for, which is what penetration is compared against.

Every World of Tanks term