In a way, this is even more confusing now. (Not to mention the term "gun" being used elsewhere for something very different.)
I suggest renaming this TROOPTYPE to "Artillery" (though it's still not ideal if Flak Gun / SAM Launcher are concerned too) and the Artillery model type to "Towed Artillery" (since for the modern kind of artillery, it's going to be at least towed around by some kind of (xeno?)beast of burden, not by infantry itself ! Or would that be confusing because it would seem to require dedicated player-controlled trucks ? I guess that there's no way to fix this inconsistency, really...)
Originally, the word "artillery" referred to any group of soldiers primarily armed with some form of manufactured weapon or armor. Since the introduction of gunpowder and cannon, "artillery" has largely meant cannons, and in contemporary usage, usually refers to shell-firing guns, howitzers, mortars, and rocket artillery. In common speech, the word "artillery" is often used to refer to individual devices, along with their accessories and fittings, although these assemblages are more properly called "equipment". However, there is no generally recognized generic term for a gun, howitzer, mortar, and so forth: the United States uses "artillery piece", but most English-speaking armies use "gun" and "mortar".
And maybe rename Anti-Tank Gun to Anti-Tank Cannon ?
A howitzer /ˈhaʊ.ɪtsər/ is generally a large ranged weapon that stands between an artillery gun (also known as a cannon outside the US) – which have smaller, higher-velocity shells fired at flatter trajectories – and a mortar – which fires at higher angles of ascent and descent. Howitzers, like other artillery equipment, are usually organized in groups called batteries.