Nowhere near that much. 20 lbs at most.
Well I read the history about the Thompson and the reason they went to “stick magazines” was because of the weight of a full drum magazine which when loaded plus the gun weighed in at 50 pounds.
No kidding. 50 pounds? Can you imagine packing that sucker around along with a couple spare drum mags? Reminds me of Don Rickles in Kellys Heroes hoisting the 30 cal. “This thing’s as heavy as one of Kelsy’s burgers.”