Germany, 1936-1945 (209MB download, please be patient!)
The 37mm PaK 36 was the German AT gun at the beginning of the war. While it was initially effective at taking out enemy threats, they ran into trouble when faced with heavier British, American, and Soviet tanks. Despite this they were still used, although they were equipped with a new HEAT round that was inserted onto the front of the barrel and fired with a charge, which deprived the loader of protection during loading in exchange for increase penetration.