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Ricochet and Normalization

Work in progress

This wiki is still being written. Pages are incomplete, numbers may change, and some mechanics are not covered yet.

Every shell has its own ricochet angle. Pass that angle and fail to penetrate and the round skips off, keeping a fraction of its penetration and speed. Overmatch cancels the whole thing.

The angle gate

A ricochet is only possible when the impact angle exceeds the shell's own rated ricochet angle ρ\rho. Angles are measured from the surface normal, so 0 degrees is a square hit and 90 degrees is a graze.

ricochet possible  ⟺  θ>ρ\text{ricochet possible} \iff \theta > \rho
The ricochet angle is a per-shell config value, so it varies from shell to shell.

Shaped charge jets are treated differently. Their gate is floored at 85 degrees:

ρchem=max⁡(ρ, 85∘)\rho_{\text{chem}} = \max(\rho,\ 85^\circ)
HEAT and chemical ATGM detonate on contact unless the hit is a true graze, whatever their config says.

Interactive

Bites in Impact angle is within the ricochet angle. Penetration is then checked against the effective thickness.

What happens on a bounce

Passing the angle gate is not enough on its own. A shell that fails its penetration test ricochets only if the plate is not overmatched. If it is overmatched, nothing can bounce it. A failed penetration on a plate that also fails the ricochet check means the shell is absorbed and does nothing at all.

P←P1.3,v←v1.3P \leftarrow \dfrac{P}{1.3}, \qquad v \leftarrow \dfrac{v}{1.3}
A bounced round keeps travelling with both its penetration and its speed cut.
d⃗out=d⃗−5 (d⃗⋅n^) n^  +  random cone of about 1.08∘\vec{d}_{\text{out}} = \vec{d} - 5\,(\vec{d}\cdot\hat{n})\,\hat{n} \;+\; \text{random cone of about } 1.08^\circ
Note the factor of 5. A mirror reflection would use 2, so the round is thrown further away from the plate and leaves at a steeper angle than a true bounce.

Gates by family

FamilyGate used
AP, APHE, APDS, APFSDSThe shell’s own RicochetAngle
HEAT, chemical ATGMThe larger of its RicochetAngle and 85 degrees
HE, HESHThe shell’s own RicochetAngle
Because the value is per shell rather than per family, two guns firing the same shell type can bounce at different angles.

Overmatch cancels ricochet

When a plate is overmatched the ricochet branch is skipped entirely, so the round cannot bounce no matter how steep the hit. The overmatch test compares calibre against the plate's raw normal thickness, without the armour multiplier applied.

CM>t,M={3AP, APHE6APDS, APFSDS7HEAT, ATGM\dfrac{C}{M} > t, \qquad M = \begin{cases} 3 & \text{AP, APHE} \\ 6 & \text{APDS, APFSDS} \\ 7 & \text{HEAT, ATGM} \end{cases}
The full overmatch rules, including how it also bypasses the thickness check and refraction, are on the penetration page.

See also

  • Penetration : Whether your round punches through, and how angle and range change it.
  • Armour and Protection : Slope, composite, spaced, ERA and NERA, and what actually stops rounds.
  • Shell Types : AP, APHE, APDS, APFSDS, HEAT and HE, and what each one is for.
  • Ballistics and Trajectory : Shell drop, velocity loss, and leading a moving target.
  • Reload : How the base reload turns into the time you actually get in game.