I know the M&A people personally. They are good guys, one of the guys at M&A has been in the business foe over 40 years. He's one of the guys I hang out with at the IL gunshows while we have coffee in the morning before they let the herds in. M&A parts are no different that Bushmaster. Hold up a Bushy upper to an M&A upper and find a difference, I'm sure someone here will have a comment on that, but there is no difference. I have abused M&A stuff, no problems. My girlfriends M4 is all M&A on a Bushmaster lower. It has seen 3k plus rounds without a hiccup and very accurate too. I have mostly M&A lower and small parts in my extra parts bin because I trade with them at gunshows and have forever. If I need a firing pin, or detent or whatever, It's M&A from my own stock. If I need something else, I can ride my mountain bike over there.
Some cool places all within 10 minutes of my house:
DSA
Krebs
M&A
Model 1
A couple hours from home:
Rock River Arms
Springfield Armory
Armalite
Le Baer
I am always at a loss for why IL is such an anti gun state politically, we build all the guns!!