Both style of RPD belts are with out a doubt some of the easiest to load by hand, once laid out straight on a table just as fast as an M16 magazine. For the record there is an extremely rare East German multipurpose belt loader called the Gurtfuller 64 adopted for service in 1964, and is capable of loading different belts in calibers 7.62x39, 7.62x54R and 7.92x57. It will also fill AK47 magazines as well. When I receive mine, I'll report back on its function and fit.
Mark