you see, comrade. When tank ammo has no explosive in because we sold it for potato, ammo can not explode when western spy tank shoots it.
TL;DR the higher the post pen damage the greater the potential for igniting ammo. For example a shell with 150mm of pen (at impact) vs ammo behind a 90mm has a higher chance of detonation when compared to 105mm of penetration vs ammo behind that same 90mm plate (assuming lab conditions and no angling)
I don’t have any evidence on hand, and I may be misquoting a youtuber.
I’m fairly certain that a major factor is the amount of energy left in the shell post penetration is a factor. I’ve blacked out ammo with a direct armour hit and it not explode. My understanding and personal rule of thumb is that you need to “Overkill” the ammo, if shooting solid shot, apcr, apds, apfsds etc. You need to have enough excess penetration to ensure the penetrating parts will not only destroy the ammo but also ignite it.
I believe HEAT shells function along a similar logic, Ie. if you shoot a 90mm heat shell and it penetrates the equivalent thickness of 300-350mm of armour the post pen effect is going to be next to zero.
When using APHE shells and over pressure I’m never actually sure what delivers the killing blow, if its initial spall from the penetration, shrapnel from the shell charge exploding or the explosive effect itself.
I have more or less given up on HESH as a viable ammo type and have nothing to contribute.
I don’t think it’s as simple as RNG, or rather there’s a probability of a piece of ammo exploding on hit.
Translation to english: The carousel ammo cannot explode if you do not hit it.