Am I correct in my understanding that there are very few AR15 Upper and Lower "manufacturers" and that they supply these items to the various companies who "finish" them by engraving whatever on these parts and apply whatever "coatings", etc  to these parts?

If I'm correct... who are the higher quality "manufacturers" ?  

OR..... who are the companies ("finishing companies") that sell  the higher quality Uppers and Lowers?

You’re mostly incorrect.  Tons of companies machine receivers.  There are only a few forges creating blanks, but the stuff that truly matters is done by the manufacturer doing the machine work on that forged blank.  Those are pretty much countless, probably 100+.

That’s not even touching factory billet receivers, which are just machined from bar stock, in many cases by individual manufacturers.

Bottom line, if you’re just looking for good quality, in spec receivers, you can essentially take your pick of forged receivers from any widely known manufacturer.  I’d probably recommend staying away from no name places, same for anything small time and local (unless you really trust them).  

If you’re looking for particular feature sets that go above and beyond basic, I’d find a few that fit your needs and do your research from there.

Thank you. Would Aero Precision be considered a High Quality supplier?  Being in "spec" is my biggest concern.  I'm looking at forged Uppers and Lowers.

Aero M4E1 is a great lower and has some nice features.  

Do some searching, you can find them for around $100.

If you buy from someone reputable, I wouldn't worry to much about in-spec.  PSA has their own brand of lowers that go on sale for $40 or so.  And Anderson is about the least expensive - lots of members here are happy with them.

Actually the term I think you mean are "forges".  There are only a few forges that produce the forgings that become receivers.  With modern CNC machining tech it doesn't take anything special to produce a finished receiver that is within spec.  Q/C , or lack thereof, is what generally separates the good from the not so good.  I've built on several and all went together as they should and all functioned as they should.  There are differences in surface finish and fitment between receivers, but nothing that affects function.  Anderson, PSA, Aero, Willow, 17D, and a couple unknown mil-spec A-1's.  It is easy to overthink this.

I used to talk up Aero but I had a pretty crappy experience with their cs last time. They need to work on that.

IMHO, Aero uppers and lowers are GTG.  AR-15 and AR-308.  Been using them for years, from 2015 on.

I buy them only when they're on sale from any of the vendors, which is frequent, and also their BLEMs are GTG.

My Aero upper and lowers have been fine in every way.

There's a small number of foundries which forge the receivers to the 0% level.  

Aero Precision has been known to mill or finish uppers and lowers for other suppliers.  There are probably other companies doing this, but I haven't heard much about any.

I own couple of Surplus Ammo and Arms lowers which were clearly made by Aero before their name became popular.  SAA would sell their own branded lowers cheaper than the Aero lowers

No reason to spend more than PSA or Anderson unless you just gotta have a rollmark.

Or one of us unfortunates that shoot from the wrong side.

I'm a lefty and use exclusively stock forged receivers, just with the common ambi parts so as to keep compatibility with standard parts.

@SteveOak
@WrenchGuy

My son shoots lefty due to eye issues. Besides Stag:

Who are good manufacturers of lefty uppers + lowers?

What are good ambi parts for 'right hand' lowers?

Thank you for any insight.

As stated above, I only use standard lowers and uppers, though I do have some uppers without a forward assist for target or longer range use.

- Radian Raptor is what I consider the de facto standard in ambi charging handles, most of my ARs have this.

- Troy is my preferred ambi magazine release, though there are many options here. I prefer the Troy simply because it moves the release lever down and away from the bolt catch to avoid a mix-up on these two controls.

- P.O.F. offers their Universal Bolt Catch which is simply a standard bolt catch with a larger lower pad to allow manipulation with the left trigger finger, much like we usually do anyway but it makes it far easier.  There is also the PDQ lever though its design is obviously done by and for right handed users so its a big NOT recommended from me.

- Forward controls has a really nice forward assist that deletes the raised rim around the end of the button, making it perfect for left-handers, though its pricey. The older tear-drop forward assist button would accomplish the same thing at a much lower cost.

- Ambi safety selectors are offered by many companies so its really up to what you prefer. I recommend trying a cheap one and then if you don't like it, upgrade. That said, my favorites are the (expensive) Radian Talon, (mid-priced) Damage Industries ambi safety, and (cheapest) any very basic $10-$15 stock looking lever set. (yes, I have all of these myself)   To further expand on this, I prefer the Damage Industries option as they can be had in 45* or 90* with medium or short levers, very much like the complete kit from Radian, but at a significantly lower cost. I prefer the 45* with medium levers.



Keep in mind, this is by no means an exhaustive list, just my preferences after years of trying different options as a life-long lefty.
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WOW! Thank you for the extensive input.

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You are certainly welcome!

However, please also check what other members have to say as they may have info on other stuff that I don't, its always a learning experience.

I built mine on a Mega Arms ambi; MEGA AR15 BILLET GTR-3H AMBI RECEIVER SET

Radian charge handle.

Adams Arms piston to avoid a face full of gas.

You get used to the brass flying in front of your face. LOL

Rock River Arms


https://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_ID=13