M16's are very reliable. The upper is a scratch built using a CMMG stainless 22lr bolt set with a Spikes auto trip set el chepo flattop upper from midway a one piece forend and a YHM mite FA rated 22lr suppressor. Runs great. I can even run a 50 round black dog mag ( the ones I used here ) with Remington subs and it still runs perfect.I'm surprised at how well everything fed in your MG.
I'm lucky to get 10 rounds fired off in my 22 auto pistol without a hickup.