When the Yugoslav Peoples’ Army began AK development, they produced the M64 infantry rifle and the M65 support weapon. The M65 had a longer and heavier profile barrel and a bipod – and in its very early experimental iterations a quick-change barrel mechanism and a folding carry handle. By the time it entered regular service it was the M72, the carry handle was gone, and the barrel was fixed in place.
The internal parts of the M72 were interchangeable with the standard M70 rifles, and they could also use the same magazines – although a drum was made specifically for the M72 to allow more sustained fire. Note that like the M70, the M72 originally had an automatic hold-open for empty magazines, but this was removed to allow compatibility with standard AK pattern magazines. The original M72 used a distinctively shaped milled receiver like the very first M70 rifles. Two later versions would follow; the M72B (slab-side milled receiver and pinned barrel) and M72B1 (stamped receiver).
Thanks to Polenar Tactical for arranging access for me to film this excellent example of an early M72!