Well, sort of.
Disclaimer: I'm not an H&K rifle buff, but my friend is. Don't be too harsh if I'm mangling the nomenclature. This is not my rifle.
Here's his PTR91 belt conversion. The full-auto trigger pack (or whatever you call it) came in at his dealer, and while the paperwork hasn't cleared yet we did get to try it out on the range out behind the dealer's shop.
This was my first exposure to belt-fed machineguns, and when they work, they're a hoot. When they don't, not so much. The big problem we were having is the weapon would fire, eject, feed the next round into the chamber, but then FTF (no hammer fall i.e. pull the trigger and nothing). That, or the we'd get a double feed (one in the chamber and one trying to strip from the belt). We never figured out if the hammer wasn't cocking, the sear wasn't resetting, or what. We could manually charge the rifle, eject an unfired round, and then the next round would fire, effectively turning the rifle into a single every-other-shot. On the good side we did get pretty damn proficient with yanking the feed box, pulling the double feed, and getting back in action. On the bad side, it's a pain in the ass to do that all the time.
At any rate, it was a blast when it worked, and shooting belt-fed is FUN!!.
ETA, here's a short vid...
That is what I want. Belt fed full auto 308 goodness, swappable barrels.
From watching the vid I don't know if this is true with HK belt feds or was even true about the ones we used but in the army with the m240s and m249s they always told us to have longer bursts as it was easier on the gun and the seer. In basic we had to yell, "Die terrorist die!" or "Kill a family of five." when we pulled the trigger each time to make sure it was long enough. Might be something to try cause those burst were awful short.
And belt feds can be a bitch when they jam that's for sure had one once were a spent link got jammed in the barrel and bent up into where the bolts locking lug was supposed to go and I had to try to figure out what the hell was wrong in the dark by feeling cause nods suck ass up close.
Glad to see some MM-21's are making it out there. How long have these been on the market?