There was a project for a new 10.5cm anti-tank gun.
However only prototypes were developed and the 12.8cm was chosen instead, as it could be used as field artillery as well.
So the gun and ammo existed but nothing ever came out of the project, apart from the proposal for a more powerful armament for the Tiger II.
I like to visit such threads. I always find something very unexpected :D
Edit: OH MY GOD, APFSDSHE-T :D
Edit2: does it have tracer? Can’t tell. But it should. Also ballistic cap would add 2 more letters, will have to look it up again tomorrow. I doubt it’s capped, but best case scenario would be the ultimate APCBCFSDSHE-T
Or launch something at enemy capzone (shooting it at a spawn is pointless, at 100m/s it would take like 1 minute to get there, and that assuming it even has range to do that, and it doesn’t).
I mean, this one when fired at 45 degrees would go almost 1000m, so that’s like 8 times better than Churchill *etard. Still rather useless, but also pretty funny if you manage to lob it over buildings and hit somebody.