Recently I've been having fun putting 17-pounder and KwK 42 into Inter-war period heavy tanks......
The thing is that those two guns would likely be low on availability during World War 2 unless you are either a British Commonwealth member or a neighbouring ally of Germany.
Bofors has a 75mm AA gun that was copied and then made into a tank gun by Japanese, but it seemed closer to American 76mm gun; it did become comparable to the 75mm gun on the AMX-13 when the Swedes did their own conversion post-WWII for their Strv 74 programme.
Which leaves shaped-charge projectiles that don't need the kind of velocities possessed by the 17-pounder or KwK 42. Finland went down that path, and the result (114mm HEAT projectiles used on BT-42) ended up rather useless- which comes as a surprise to me since Finland copied a German design, and Germany seemed to be an avid user of shaped-charge projectiles precisely to deal with the likes of T-34 and KV-1.
So...... what did it take to make a good HEAT weaponry in World War 2? And who, other than Germany and Soviet Union (which is said to believe in anti-tank capability for their howitzers via HEAT projectiles, too), could be relied on to create serviceable shaped-charge projectiles? Thanks in advance.