????????????????? The Madsen M50 is a 9mm SMG. The seller has no idea what he has. The gun on GB is a Madsen 1904 LMG. They were made in a potful of calibers 7x57, 8x57, .30-06, 6.5x55, .303 Brit, 7.62x54R etc. Probably can be converted to .308
https://www.youtube.com/watch?v=3CP40hN0dEM