A few updates...
Had our first warm game in May (lots of April snow on the first game) and the MK46 performed beautifully, despite running down all my batteries. So in early June we had a tech day and I tore open the gearbox. Everything seemed fine until I was reassembling it and re-checking shimming, I noticed the gears would move normally and then bind to the point where I could not turn them by hand. So after fixing this and relubing everything, the MG was back up for the rest of the summer!
In late June at a skirmish game I ran into an odd issue that took a while to chase down... With my A&K 1500 Rd nutsack mag I would experience a jamming issue that sounded like double feeding. Sure enough a BB would roll down the barrel and the gun sounded like it was jammed. Despite clearing the barrel and reassembling multiple times, the issue persisted. My initial thought was, naturally, hop up and bucking. The bucking has seen significant use, and probably time to change out. It was... You can see the indent from the flat hop nub here.
And the wear on the inside. Note that most of this is where the bucking was modified to be a flat hop, the contact area is the dark portion near the top. Time to change regardless.
And, a new bucking installed!
After further testing, standard M4 mags and the 2400rd large boxmags fed and cycled just fine, which led down a long road of trying to solve a feeding issue with the box mag.
As it would happen, yesterday we had another tech day where I fully disassembled the nutsack mag, tested various fixes (which worked to varying degrees, but none solved the problem entirely). After a long period of trial and error I removed the gearbox to have a look inside, because hey, it couldn't hurt right.... oh boy.
So what presented symptoms as a jam turned out to be a partially stripped motor pinion gear and heavily worn piston rail. I didn't snap pictures of the rail but have a look at the motor. Granted, this is after thousands and thousands of rounds, so no surprise there just a reminder to check everything when diagnosing problems.
So, took an old spare I had initially purchased for my M60, along with a new piston rail, relubed everything, reshimed the bevel gear to the spur to get it running again, and ordered an SHS high torque motor. I also replaced the trigger switch because it was original and during the last time I used it, something caused the gun to run away on full auto. It was a rainy day so it might have just been the signal wires in the mosfet getting a little moisture in there, or it could have been wear on the trigger switch. Either way, cheap part and cheap insurance.
Here is the motor, the next picture is the tooth it lost.
And here is a video from my buddies GoPro strapped to my helmet during a few skrims, shows the MK46 in action.
https://youtu.be/0F4k6Op6rjo?t=89