Only joined the forum now. Interesting that the M-21 is linked to the Galil. I know that the Serbs intercepted a shipment of South African R4 during the war period. It would make more sense that they used these examples and not the Galil when designing the M-21. Of course the Galil is itself a licensed copy of the Galil, but it has the plastic forestock parts (Galil is wood)... Stock is also slightly longer (apparently average South Africa was taller than average Israeli soldier).
Welcome to FR. Stick around, we have a lot of good firearms threads.
Wellcome.
I belive that Serbian and Israely designers went the same path, eventualy reaching the same result.