During the scene with the gun fight at the farmhouse, you'll notice that at one moment, the biggest Russian with the machine gun is holding an MG34, which he had had since he landed, and the next moment, apparently only when he is shooting, it is an MG42. It continues to switch back and forth from an MG34 (round barrel with holes in it) to an MG42 (larger rectangular barrel with slits in the side). At one point, you can see a curved cartridge hanging from the bottom of the MG42, a feature not found on such weapons.
When Hossom and the "KGB" team raid the farmhouse, Hossom has found an German made, German issued Mauser k98 behind the enemy lines of Nazi-controlled Ukraine. He then proceeds to prepare for the raid by cocking the gun pump-action style. The Mauser k98 is a bolt-action rifle, as is plainly seen shortly thereafter.
The plane referred to as a "DC3" is actually a post-war Russian amphibious airplane...a BE12
The Russian team to rescue the Jewish scientist is under the command of the KGB, however during World War II the KGB did not exist and its predecessor was known as the NKVD