The sub machine gun that MSgt Jigs takes back in time is an MP-40 Schmeiser. This was used by German soldiers in the 2nd World War.
Season 2 of Hogan's Heroes was broadcast as The Time Tunnel on Friday nights throughout the 1966-7 season. Whit Bissell, who plays Lt. Gen. Heywood Kirk, guest starred as General Kammler in The Rise and Fall of Sergeant Schultz (1966), which aired in competition with this show on October 21, 1966.
This is the first of many episodes where Doug and Tony encounter people who realistically shouldn't speak English, but do - in this case, Greek people from 1184 BC. This suggests that the Time Tunnel has some kind of universal translator built into it. Or it is just another example of the "English is the lingua franca of time and space" logical blind spot which was very common to 1960s TV shows.