The later SU-122 and SU-152 with better armor and bigger guns were primarily direct fire artillery that could be used as anti tank if needed.
Ah, but the SU-122 and the SU-152 did not come later. They were contemporaries with the SU-76. However both fell out of production fairly quickly, while SU-76 production continued through the end of the war.
The original call for SU vehicles included one mounting a 76.2mm gun, and one mounting a 122mm howitzer. These became the original SU-76 and SU-122.
However the original SU-76 was deemed a failure, and production ended quickly as a re-design was sought. The vehicle we popularly call the SU-76 now is in fact the SU-76M, a significant modification with re-arranged automotive layout (engines and drive train) and an open top (the original was fully enclosed). Thus the vehicle we commonly call the SU-76 did not enter production until many months after the SU-122, at about the same time as the SU-152.
All Soviet artillery was expected to frequently fire over open sights. Anti-tank work was also considered a common task for Soviet artillery, and was integrated into typical defense plans, whereas most militaries of the time considered it a last-ditch task for the occasional "oh sh!t" moment. In this, the SU-76, SU-122 and SU-152 were no different.
However, the Soviets did have formations who's primary role was anti-tank work. The SU-85 and later SU-100 were developed for this role. The requirement for the SU-152 is also often suggested to be due to the need for a heavy anti-tank platform, though over time it certainly became a preferred platform for reducing prepared defenses.
While tanks (and SUs) were classified as light, medium, and heavy for logistics purposes, their combat roles were conceived as recon, infantry support, independent operations and/or breakthrough. Contrary to the British model, and more in-line with the French model, in the Red Army an infantry tank was a light tank. What the Brits called an infantry tank was to the French and Russians a breakthrough tank. It all worked through in the end, though, as the Matildas and Valentines which the Brits called infantry tanks (thinking they were heavy tanks) were considered light tanks by the time they got to the eastern front.
The SU-76, as a "light" SU, was considered an infantry support platform. In this it was expected to supplant, and eventually replace, the T-26, T-60 and T-70 (on which it was based) light tanks. The "medium" SU-122 was originally envisioned as direct-fire artillery to support the independent operations role (the tank and mech corps). Over time it was determined that the primary fire-support need of these formations was defense against counter-attacking tanks, and so the SU-122 was abandoned in favor of the SU-85 (and later SU-100). The "heavy" SUs, the SU-152, later ISU-152 (and ISU-122) were envisioned to support the breakthrough role, working with or in place of heavy breakthrough tank formations.
Of course, in action it could all get mixed up. But as I understand it that was the thinking that went in to the design requirements.
The SU-76 was never well regarded by anyone except high command. Contrary to many wargaming rules (which seem to want to give it SOME redeaming benefit) it's gun, while different in detail, fired the same ammo for the same performance as a T-34. It offered no advantage in firepower in the AT or infantry support role, and was at a grave disadvantage in terms of armor and mobility. But it could be built in the GAZ automobile factory (which had produced the majority of T-60s and T-70s), a factory which was not able to product heavier AFVs. And having a mobile, bullet-proof 76.2mm gun to support infantry attacks by shooting up MG nests and dug-in enemy infantry was better than not having one, and so it stayed in production through the end of the war, and was built in larger numbers than any German AFV.
So while it ain't much of a weapons system, if you put more of 'em on the table than any of your opponent's German tanks or AFVs, and send them one way to support an infantry attack, while on another path you send your T-34s and medium SUs, which also outnumber all of the the German AFVs together by a factor of 3 or 4 to 1, behind a breakthrough wave of ISs and heavy SUs which outnumber the German heavies by 3 or 4 to 1, you may find that your SU-76s are remarkably successful.
At least the Russians did.
-Mark
(aka: Mk 1)
been building and painting his own army for Flames of War for a while now.
