Ok. I've hit a wall here. My M&P 15-22 is failing every other round.
It's not:
Dirty
Mags
Firing pin
Feed lips
Extractor
Ammo
Trigger
This gun has 48,000 rounds through it, it's a very simple design. I'm out of ideas. Replaced firing pin.
When it fails, I can open it up and see that the...
Yea, the Dremel with the right heads and some water will pull that black off in about ten minutes. You will then need to polish it with some dremel buffer heads and a good polish. I use Blue Magic metal polish cream. It works great.
I've polished many AK bolts down to a chrome finish. Looks cool. Doesn't work any better. Smoothing out the trigger will fix your sticky bolt though. The dremel is the way to go. When I get home I will get the name of my polish that worked real well.
Use these heads (pic) plus water to pull off...