Thank you for the explanation, Alex!
What i`m more interested in are the “front” ones, and more specifically, how much importance does the penetrator have in the ignition of the compound (actually, the compression provided by it).
There used to be, especially in large coastal artillery pre-1900 some armor piercing shells that were filled with black powder (or in some cases, black powder mixed with aluminium powder) that would ignite themselves on impact without a fuze. The explanation provided in the era is that the intergranular friction upon impact generates sufficient heat to auto-ignite the filler. That seems a bit far fetched but at the same time it could be possible, but maybe just in very large calibers (>150mm)… I was wondering if this principle is true, and whether or not it could work with incendiary compounds found in modern era ammunition (12.7mm and bigger). With or without the penetrator providing compression.
I think it also depends on what the incendiary compound is used… Too many variables.