AT-Rifle Team
The AT-Rifle team is a unit in Flames of War availble for the German army to recruit. In reality, German AT-rifles were largely an ad hoc collection of captured equipment, outdated weapons, or typically overengineered weapons that were introduced just to late to be relavant in the battlefields of WWII.
IRL
The Origin of the Anti-tank rifle starts in the battlefields of WWI. See, there were these big fat MEHTAWL BAWKSES called armoured cars, which the Germans and allies hated very much. Early attempts by both sides to make standard infantry rifles work as At-rifles range from interesting but overdone to laughably terrible. By the time even the kinks in these weapons had been ironed out, the Germans brought up their own solution: Just manufacture a dedicated rifle that only shot armored vehicles, the Muaser M1918
While it had a good chance of breaking the firer's collarbone and produced a ton of noise, the design was surprisingly effective. After the end of the war, AT-Rifle development slowed, with very few actually being developed outside of Poland, Britian, Germany, and Finland. The most likely weapons you'll be looking at on these models is the Panzerbuchse 38 (a renamed Mauser M1918) and 39(an improved version).
The design was relatively straightforward: combine the idea of a bolt action rifle and a breech loading cannon, strap it into a system that can be fired from the ground, throw a big fucking round into the gun, aim at a tank, and turn the occupants into mush. However, this was extremely complex, and several other nations had already improved the concept with 5 round magazines, along with making them far more mobile and less likely to destroy your arm when firing.
In spite of its shortcomings, they were retained until 1944, when armor technology had exceeded the ability for the AT rifle to remain relevant, and was phased out in favor of more powerful weapons such as the Panzerfaust and Panzershrek. Today, the AT rifle is still in service as an "anti-material rifle", which is really just a cheaper alternative to chucking a guided missile at a target like a truck or car.