What is the weapon/prop used in S8-E4 'Some Guy'? (Spoilers for S8-E3 and S8-E4)

>!The Saviors are shown disassembling the M2s for transport and boxing them back up after ambushing King Ezekiel's regiment, but I've never seen an M2 with that internal barrel extension coming out of the barrel support/heat shield, as is visible once they remove the barrel, and I've dealt with plenty of real-world M2s in my life. IMFDB is no help, is this a niche model of M2 or clone, or a purely prop model?<!