The type of shell that a given tank carried was determined both by tank technology (see: barrel length and construction), tank role (an infantry tank would have different ammo than a tank destroyer) and by its country tank doctrine/tactics (so how the tank has to be used in coordination with other forces). Most of the main battle tanks carried them both, while infantry tanks preferred high explosive and tank destroyers preferred AP rounds. But mot of the armored forces carried them both , even if in disproportionate numbers. Changing ordnance types wasn't suh an issue, since both rounds would have been interchangeble for their cannon chamber size, were easy to tell apart for overall sizes and colours, and were usually stored in separate compartments of the tank.