Getting ready to change into someone more comfortable. Name changes coming.

I definitely agree that that's a better way to do it, I just didn't think that was what the shop that finished the lower had in mind, so I was trying to make sense of that strange modification.  Thanks a lot for posting that - I have a number of Wheeler tools but missed that set, so I'll definitely be ordering it.  They look a lot more sturdy than the Brownells bolt catch roll pin punch I've been using.

I thought it might be something like that at first, but it didn't make sense to me that the groove would only be on one side.  I think the other guys are right that it was done to allow better access (or so they thought) for installing the bolt catch roll pin.

I might have missed it in this thread, but I have not seen Noreen mentioned. They sell quality 80% lowers in small and large frame variety. Good stuff made in the great state of Montana.

I have a couple of guns made with their lowers and uppers and they are GTG

I finally found a plain MILSPEC lower with no strange modifications - the Anchor Harvey forging from Delta Team Tactical. My only minor complaint is that the lip around the magwell is very “chunky.” It seems much heavier than other lowers. I might see if I can have it re-profiled a little.

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3-ACR
I've been following this thread, and a few others, for a while.  I too, am interested in the differences in forgings used by AR manufacturers.  There are at least five "Post-A1" types with reinforcements that were/are used.  Possibly more.  And, there are variations among those five, especially the first one.  I have raw forgings (0% machining) of the first three, and an 80% of the fourth.  I would post photos, but don't have a host web sight at this time.

The first is the A2 forging originally used by Colt with the "fading" rear reinforcement, and intersecting "tunnel".  It was also used by Balimoy, and Eagle Arms (before Armalite).  The example I have has forging numbers in the un-machined grip area, but nothing that easily identifies the manufacturer.

The forging that you have been looking for is the second one.  It has no "tunnel" for the takedown pin spring at the rear, and was made by Kaiser Aluminum.  It has "KAO-11" in the grip area. (I've seen numbers other than "11").  I have/had finished receivers from 1995(PWA & Bushmaster), & 1998(Olympic) that used this forging.

I don't remember ever seeing 80% receivers of either of these first two.  I could be wrong.

[Had to split post because of character limit]

The third is the Anchor Harvey forging.  It has the short "tunnel" at the very back end of the rear reinforcing. (There is actually also a short "tunnel" at the front before machining)  Again, my raw forging is identified in the grip area with "A213" ("A" is split horizontally).  These are still around, as finished receivers (Colt, Bushmaster (Ilion), and others), and as 80% receivers.
[I have recently seen a photograph of this raw forging but with a Cardinal Forge symbol in the grip area]

The fourth is the current "full tunnel" Cero forging used by just about everybody, with the "keyhole" identifier on the trigger guard leg. (although, I've seen it on the mag well, as well as no keyhole)

The fifth is the forging like the 80% receiver you had from Right to Bear Arms, with the heavy flared reinforcing at the rear.  I've only seen photos of FN M4s and A4s that use this forging.  And, I don't have any information on who supplies it.

I hope this is helpful to anyone looking for a particular forging.  And, please comment or correct me if you think I got something wrong.

@Dex223

If you want get 3-ACRScout's attention- do it like this:  @3ACR_Scout

He's a Team Member who has posted in this thread, so is automagically subscribed to it.  No need to @ him.

@backbencher

I did not realize that a member is auto-subscribed when they post in a thread. News to me
But isn't that different than using the @ symbol to create a "mention"?
Whenever a "mention" is generated with my username, I get a popup box, notifying me of what thread to go to.
Unless 3ACR_Scout checks his subscription list, he'll never know he was mentioned in a thread?
Am I correct?

Correct.  But if he checks his subscribed threads, he'll see there was an update.  It's annoying as hell to be @'d to a thread you're already subscribed to.

I see.

Dex, thanks a lot for posting the breakdown of the lower forgings.  That matches what I've seen, but I wasn't sure how many variations were out there.  I used the later Cerro "full tunnel" style of 80% lower to clone my first Army-issued Colt M4 (made in 2004) before I knew about that selector detent variation.  I can see now in my old photos that it had the "fade" and short tunnel at the back.  I'm not going to worry about it at this point, but I find it interesting to look for those details.

For the early M16A2 lower, I think I'm definitely going to have to modify one of the later style lower forgings to look "close enough," since there doesn't seem to be any comparable 80% lower available, as you noted.

As far as the subscribing goes, it doesn't appear to automatically subscribe you when you post, regardless of membership.  My only subscriptions are the ones I manually selected, and this thread doesn't appear as one of them.  The "Subscribe" button is still visible at the top to give me the option.  I just noticed that someone had posted a new reply to this discussion when I checked the "Build It Yourself" sub-forum for updates.  I do see the little green arrow next to each topic that I've previously read, but I don't get any notifications from this one.

@backbencher
@alpharomeofifteen

Thanks for the information about using "@" to get someone's attention.  I did not know about that function.

@3ACR_Scout

No problem.  I only wish i could post photos; then I could show you the differences.

There is a really good post at the top of the A2 Build discussion on lower variations.
M16A2 Lower Forgings and Variations

Are most new 80% lowers going to be the style that don't require using punches or roll pins?  Everything mostly threaded?  Getting the urge to build a new 80% but would like to stay away from using punches if possible.

Just buy the rubber coated LRBHO flat roll pin punch and starter and it's easy, and I say this as a guy who took advantage of GWACS' warranty b/c I broke a LRBHO boss off before I had the proper punches.

Ya, I need to invest in the rubber coated ones.  In the past I've improvised using 1/4 bits from a security bit set.

Anyone know of a 7075 lower with the mag release fence for an ambi release?  Only ones I've found are 6061.