I may be wrong, but I don't think Flemming ever did an HK52 type conversion. As I understand it, he developed the HK51 conversion of a G3, but never messed with the 52 in 7.62x39. HK made a few prototypes but they never went into production. Toad Bailey of special weapons notoriety made an HK52 type, but only made a few and, from what little I've heard, they didn't work all that well.
Honestly, if you're in the market for a 7.62x39 MG I'd be watching C-products for the release of their 7.62x39 mags for the AR15/M16, rather than considering a poorly cobbled together HK52 clone that will be next to impossible to find spare parts for.