Only lowers I had problems with was AR57 brand lowers. The rear take down pin hole was off by 1/4 inch.

This was bought from AIM during one of the last panics. AIM went through their stock and found 80% of their stock was out of spec.

My go-to lowers are by BCM but you’re looking for something perhaps a little more than milspec. Maybe billet construction? This can definitely be a rabbit hole.

Mega has always been top-notch but I’m not sure if you can get them anymore since their merger with Zev Technologies. I have one of their lowers with a matched upper and it has some of the best anodizing I’ve ever seen. I just wished they actually released their small-frame 7-lb .308.

One of my favorites in terms is machining quality has to be 2A Armament. I have one I’m currently building with the specific goal of being ultra lightweight, somewhere in the 4.5-5-lb range.

ADM has one of the best ambidextrous controls if you’re looking for that; it actually has a right-sided bolt hold which most don’t. Really good customer service, too. I have their Mod 2 receiver set.

KAC, Radian, and LWCR all have truly ambi controls, as well, but I don’t have these so can’t really comment on them.

My BIL has the billet Spike’s Tactical receiver that looks great.

My next build will be on a PWS Mod 2 set...those are nice!

Matching 5.56/.223 & .308 receiver sets that I don’t have but I’m eyeing real hard:
1. Aero Precision M4E1 & M5E1 sets
2. SLR Rifleworks billet sets
3. Ascend Armory billet sets

Why these receiver sets? Well, I have all the milspec receivers I could want including a factory built BCM at my bedside. I use it for training and in classes. It’ll always be my go-to rifle. But sometimes building something with a little more flavor helps to break up the monotony.

I want to thank all of you for sharing your knowledge.

Sounds like Aero Precision has a quality product.

There's only a small handful of AR receiver manufacturers that actually make them. The rest just contract with those few manufacturers to have them fabricate the receivers on their behalf.

I've had good results with Aero Precision, one of the actual fabricators. Aero has been around for some time as an aerospace parts manufacturer but one would have to say is sort of relatively new to the receiver business (over decade or so). In that time they've captured a sizable share of the OE market as a receiver fabricator for other companies as well as for their own branded pieces. Spike's, PSA, Armalite, NFA and a host of smaller brands have contracted currently or in the past with Aero to have them supply lowers and uppers. The builds that I've done with Aero-sourced receivers have all been solid with no tolerance or fitting issues.

AFAIK, I've only used receivers made by Aero, ZEV (formerly MMS, or Mega Arms) and Anderson. All were made to proper spec as far as I can tell; mags fit and lock and drop free, no issues swapping uppers around, etc, parts kits and furniture fit as they should. I'm not aware of anything I have that was made by CMT or LMT, but who knows for sure? There's seems like a lot of musical chairs is played in this game where receiver companies contract with whichever fabricator can fulfill their orders in a timely manner and to a quality level that they'll accept.