I was about to say the same thing. With a stick mag, they are 12 pounds, with a drum it is a real bar-bell.
I’ve got a semi-auto version of the M1A1 Thompson which wasn’t made to accept drums (neither were the military ones). The weight for the one with 12” barrel was 11 lbs. With the 16” barrel this one has, it weighs a little more.
It would be a real work out for Arnold..... Arnold Stang that is. The other arnold, he can hike his sorry ass back to Austria.