The M&P is probably the best rifle around the $600 price point. Most reliable and least amount of issues, when compared to similar manufacturers like Springfield, PSA, Ruger, BCA, current DPMS, Omni, and such.
If you like the M&P, it's not at all a bad option. Get it, slap an optic on it, a...
And they're still building and selling their regular upper recievers. The MK2 reciever has compatibility issues with other manufacturers' lowers. It was simply BCM improving a design, not at all because they had issues.
I mean, they designed a stronger receiver, moved the forward assist, and designed it to help divert gas away from your face. It was because they were having their upper receivers actually break. They use Brass Aluminum Forging Enterprise and Cerro, which are used by many of the same caliber...
A couple of years ago, they posted a video of one of their guys assembling an upper. The video, of course, made its way around the AR community. If I remember correctly, no grease, no torque wrench, no torque specs, a pipe for a cheater bar, and possibly an adjustable wrench.
Yeah, but figured that if people were going to spout out bad advice and bad parts, may as well try to rectify it. I would not advise that someone build their first AR. Buy a decent AR, optic, light, sling, train, and call it a day on it.
First things to add to a rifle are a quality optic, a quality light, and a sling. Other than that, put as many round through that thing as you can and get uses to it.
Palmetto State Armory (PSA) can be okay, but with their quality control and assembly practices, getting something out of spec or badly assembled is more of a possibility.
SOLGW and BCM make excellent stuff, and can be found right around the $1,000 mark. If you are willing to wait and watch...
Here's a lost I made of manufacturers for parts. Many of these companies also have their own complete rifles.
Receivers:
Aero Precision
Sons of Liberty Gun Works
BCM
LMT
Radian
LWRC
Zev
Lower Parts:
Modern Armory
Forward Control Designs
Sons Of Liber Gun Works
Sionics
BCM
Barrel:
Sons of...