@Baron:
Is it correct to say Anti-tank Artillery, even if ATGun is only a direct fire weapon?
In artillery jargon, a “gun” in the strict sense of the term is always a direct-fire weapon, meaning a tube artillery weapon designed to shoot at an elevation between 0 degrees and 45 degrees. A tube artillery weapon designed to fire shells at land targets at elevations of 45 degrees and higher (meaning an indirect-fire weapon) is called a howitzer.
“Anti-tank gun” is (to my knowledge) the commonly used term for the type of weapon we’re discussing here. It’s possible that such weapons are also referred to as “anti-tank artillery” (though personally I’ve never heard the term used) because they’re artillery pieces and they’re used against tanks…but as far as I know, the more usual practice is to call these things anti-tank guns. It’s a bit like the practice of calling submarines “boats” rather than “ships”, even though one could plausibly use either term.
One thing to be careful of, however, is this. As I said, it would be reasonable to argue that an anti-tank gun could be called an anti-tank artillery piece because it’s an artillery piece and it’s used against tanks. It would, however, not be correct to make the opposite argument: that all artillery pieces can be considered anti-tank weapons. Not all artillery pieces are capable of being used against tanks. Because of their operational characteristics (their sighting mechanism, the speed at which they can be trained, the elevation of which they’re capable, their rate of fire and so forth), some artillery pieces – especially the big ones – would be utterly or virtually incapable of hitting a tank (especially a moving one) if their crews tried to use them in this capacity. So my recommendation would be to simply stick to the straightforward term “anti-tank gun” because then it will be perfectly clear what’s being talked about.