What really makes a name brand upper or lower any better.

[LRRPF52]

LRRPF52,

What uppers (and lowers) do you prefer for your builds?

I generally order only from a select range of forged uppers now, then will measure those uppers and either match them based on barrel extension mating (tight), or reject them.

The forged M4 7075T6 uppers I have had the best results from include:


* Alexander Arms (believe it or not). I just built an upper with an AA 18" fluted barrel and AA 6.5 GREN marked upper, which had a perfectly square receiver face, and baked-on dry film lube inside the raceway. I used that same type of upper on my 12" pistol build as well. AA has one of the most overlooked, high quality 5.56 set of rifles as well for these reasons, from the work Bill did to make sure they applied the TDP where he felt was relevant.

* Aero Precision (my Aero Precision M4 with no Forward Assist does not seem to have dry film lube baked on inside the raceway)

* BCM: These guys work extremely hard to follow and ride certain edges of the TDP, to include very tight barrel extension tunnels, dry film lube, machining, coatings, 1913 alignment, etc.)

* Colt (Even old 1970s-era SP-1 uppers I've measured had a perfectly square face)

* JP Enterprises: Top-notch precision-machined forged receivers that are matched

* Les Baer: Super tight machined forged & matched sets

* Precision Firearms: Mark at PF takes precision-machined forged receiver sets to a very tight level of tolerances, and his forged lowers are one of my favorites, and currently what I have on my 12" Grendel. 50˚ funneled magazine well, receiver tensioning adjustment if desired, and overall great machining.

* Wilson Combat: Wilson Combat has been making precision-machined and fitted forged receiver sets for a long time now, with an attention to detail coming from his 1911 approach to building. His 2000s-era rifles influenced a lot of how I approached my own AR15 builds looking at fitting, coatings barrel profile, trigger work, and overall functionality

Before I even do anything with an upper, I insert my receiver face lapping tool in it and hold it up to the light to see if there is a gap anywhere on the receiver face. I just checked one that my brother had, which he indicated was from Radical Firearms. It has no dry film baked on inside, no T markings, and the face is so out of square it will require a lot of work to get there when I lap it. Very noticeable gap between the top end of the interface of the barrel extension flange and the receiver face, which would likely result in vertical stringing and imbalanced load on the bottom 2 bolt lugs. It has an "A" forge code, which doesn't reflect badly on that forge source, just poor machining and lack of even attempting to reach for the TDP call-outs.


The only reason I order some of the Aero uppers is for that no-Forward Assist option for a forged M4 on a streamlined gun like my 17.6" Lilja build.

If I were putting together a forged set right now that was not from one of the shops that leans more towards billet guns, I would get either AA or BCM.

If I wanted no FA, I would get the Aero again, but I've lately been delving more into billet sets from LaRue, ADM, Seekins, and 2A.

My days of building on forged sets for myself might be coming to an end, as I really like the features on the above billet sets.