Grendel LMG

[LRRPF52]

The 7.62x39 uses a rather large gas port diameter since the bore diameter is large, just as the Grendel uses a larger gas port than 5.56. The pressure differences also drive the gas port diameters, but the op-rod is a simple long-stroke system. Since the RPD has a gas regulator plug, that would be easy to manufacture, in addition to a new barrel. Since the RPD uses the 7.62x39 bolt face, one might only need a new barrel if the existing gas regulator facilitates optimum/functional Grendel gas pressure curves. Here's the 1961 Soviet Manual for the RPD for reference:

http://www.scribd.com/doc/31410672/Sovie...aryov-1961

The more I look at the RPD, the more it reminds me of the Bren...gas block, regulator, lower receiver, receiver, op-rod, stock...typical Soviet ingenuity.