First, let me encourage anyone interested in this topic to read Augee's pinned thread "A2 Receiver Variations" at the top of the A2 topics.  It's an excellent discussion on lower receivers.

From the beginning with the Colt 601, our favorite rifle's lower receiver has been constantly changing/evolving up to where it is today.  For this thread, I am going to refer to any lower forging from the M16A2, A3, and early A4 and M4 as a Generation 2.  You can call later M16A4s, M4s, and M4A1s Gen. 3 if you want.  During this "Gen 2", there have been four basic forgings used.

The first, is what's considered the "early Colt" forging.  Actually, there are three versions of this one, called the Type 1, 2, & 3 (by Augee) because of small differences.
This is the Type 3.  It was used by Colt for A2s and M4s, for civilian SP2s and Match Target rifles.  Balimoy used the Type 1 for replacement lowers.  I believe Eagle Arms(pre-ArmaLite) also used these for a short time.  Receivers with this forging are no longer manufactured.


The second, was commonly used by FN for A2s and A3s, and by other manufacturers for civilian ARs from the mid to late 1990s.  This forging was made by Kaiser Aluminum.  It is also no longer manufactured.


The third forging, is one that Augee refers to as a "Colt Type 4" or "Intermediate" receiver.  It looks similar to the second forging, but with two small "tunnels" for the takedown pin spring at the receiver extension. (the front tunnel is removed during the machining process.

This forging has been around since at least 2013.  It was used by Colt for Military rifles, although I'm not sure what years.  It was/is used on civilian ARs, and is currently manufactured by Anchor Harvey.  There is an almost identical forging made by Cardinal Forge. (Although, it has been pointed out that this one has a full "tunnel" similar to a Type 5 Cerro lower)
(Recently, Aug 2020, I saw at a local gun show, an Eagle Arms rifle that had this Cardinal lower)

The fourth, is one that Augee refers to as a "Colt Type 5" or "Late" receiver.  It's probably the most common forging, and the one that most people are familiar with.  It has one long "tunnel" for the takedown pin spring.  It was manufactured by Cerro, and is now no longer manufactured.  Cerro has replaced it with a forging we will talk about later.

This forging has been used by many manufacturers for both military and civilian rifles.

It's replacement could be called a 3rd Generation lower, and has been used for M16A4 and M4A1 rifles (and a version for civilian rifles).  It has a forward sloping extension reinforcement similar to the early Colt Type 3, but not the same.  Also, it does not have any "tunnel" for the takedown pin spring.
[photo to be added]

(I will be adding to this post as I get more photos loaded, and go thru more information)
(I'll also do some editing as I figure out how to make the photos larger.  I may be loading them from Imgur incorrectly)

Awesome post man. I had no idea there was such variation.

Why are they so different? I would have thought it was all spec’d the same especially if the manufacturer was given a gov contract.

Oh yes. Notice that he doesn't have the type 1 & 2 posted yet. There is even now a new type that is showing up. The why of so many variations is probably open for debate, as it could be incremental improvements, just differences in the forge dies or any number of possibilities.

Love this post, I have something coming in the mail to add to it! More on that later...

Does anyone know why the type 4 and type 5 lower forgings have flecks in the (raw) finish? It appears the FN and earlier types are more flat matte aluminum.

Thanks a lot for putting this together - very informative. I was hoping Augee would update his OP in the pinned lower forging thread, because a lot of the original image links are broken. I uploaded the images I could recover directly, and added a few, but it doesn't look like he's come back to it in a while.

It would be awesome if someone came across a stash of those old forgings. I know that Braceman (and probably others) can turn them into 80% lowers that we could finish ourselves.


This style of forging has been in use since the early 2000s. Here's a photo of my M4 that I was issued from 2016-2018. Sorry, not the best photo because of the shadow, but you should be able to see the short tunnel at the back. I called the Colt historian a few months ago, and he told me that the serial number range (W1252XX) was produced in 2003. This Anchor Harvey forging is what people should be using if they want to clone an M4 or M4A1 from the early 2000s and go the full 80% engraving route.

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Dex has clearly come across an old one, the type 3 Colt. The Colt type 1-3's and the FN intermediate without the detent tube seem to be the rarest by far.

The AH forging you posted is actually still available in some decent quantities, I believe as 80%'s and definitely as 0%'s. I have 6 of these for future projects since they seem the most adaptable for mimicking the other forgings. You could mill/sand/file off the last bit of that tube to mimic the FN intermediate forgings, and you could maybe file off enough of the receiver boss to taper it to look like the Colt type 1-3's. I might use one of my 6 AH forgings to practice doing one of these mods.



One thing I like about starting from 0%'s is that you can ask braceman (or whoever) to leave the flash in the triggerguard and on the back behind the pistol grip, though I'm not sure Colt or FN did this back in the late 1990's and early 2000's. Would be good to see some pics of original receivers in these places, both FN and Colt.

Here are two mid-production (engraved) FN A2s that I posted in the Early M16A2 Lower Receiver thread, built on the Kaiser Aluminum forging that Dex posted above. These are the same two rifles that I posted photos of on Page 2 of the pinned lower forgings thread. The first one shows the flash in the trigger area almost completely removed, while the second has a thin line of flash along the vertical mold seam.  I think it's hard to determine whether the flash should be in that area or not on a clone, because it looks like FN was inconsistent with how they finished them. The seam on the front of the magwell is interesting though - I hadn't noticed that before, and I don't think I've seen that on any commercial lowers. These photos are pretty dark - it was cloudy day, and I was asking a favor of another unit to let me take the photos, so I was in a rush.

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@mb44kar

The finish on a receiver forging varies depending on what the customer specifies of the foundry.  It can be pickled, media tumbled, or blasted.  I believe it's the pickled that leaves the "flecks" on the forging.  The Kaiser forgings I have look blasted and painted (or sealed) with some coating.

@mb44kar

Yes, the AH forging is the only one I have seen available as a 0% in the last few years.  And, there are a few companies using them for 80% receivers.  Strangely, they have become the most common 100% receivers lately (at least from what I have seen at gun shows).  And, they're the oldest design available forging.

I have the one type 3 Colt forging, four of the Kaiser forgings, and, only one of the Anchor Harvey.

I do remember the flashing being present on the early 80s era Colts back in '87-'91. I always used to wonder why it was left there and thought it looked a little unfinished.

In the last year, I have been able to acquire the three types of 80% lowers shown below:

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Will do Colt A2s and XM4 with the type on the top, FN A2, A3, A4 and Colt A4, early M4 and M4A1 with middle type, and more recent Colt and FN M4A1 with the bottom type. What you see on the dealers websites and what you get have little relationship to each other and even asking questions to make sure of what you get will still have a surprise when they show up engraved SAFE and FIRE after being told there was no engraving.....

The flashing is left intact on all mil AR’s (save for very early 601/602’s), and Colt has always left it in place on their offerings. It doesn’t affect anything to leave it in place, and to remove it is more machine time thus more cost.

William

Thank you Augee! Whenever you get around to it. I'm a sucker for these details.



I don't think the top forging is close enough to correct for Colt A2's, but the rest sounds good. Quite a list of builds to do!


I've seen it in the triggerguard of Colt A2's, but it's been removed on the front of the magwell on all the Colt A2's I've seen. See these images/auctions:

http://www.bigdog-outfitters.com/wp-content/uploads/2018/11/IMG_4570-2.jpg
https://www.proxibid.com/Firearms-Military-Artifacts/Firearms/U-S-Colt-M16A2-Class-III-NFA-Fully-Transferrable-Machine-Gun/lotInformation/55594307#topoflot
https://www.gunsamerica.com/995220305/RARE-Colt-M16A2-U-S-Property-Stamped-5-56-Excellent-Conditio.htm

So I think triggerguard: yes flash, magwell: no flash, and rear of receiver behind the pistol grip: not sure. No flash, I'm guessing?

On an unrelated note, I found this youtube video of Patrick Stewart doing an ad for Kaiser Aluminum, pretty neat:
https://www.youtube.com/watch?v=h1Lg9TpTnUI

Probably depends on how early you need to go - if you remember, the XM4 that we have documents by SN would date from ca. 1986, well before 1988 when FN gets its first M16A2 contract. Not being Marine, I don't have to go back to 1983.

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Here's that magic that came in the mail. Has some good info about manufacturers.











A Colt type 3 lower. Came with an A2 upper, also 0%.

There's a marking on the other side of the pistol grip, MMA, which must mean Martin Marietta Aluminum, based on the A2 upper which came with it. Forge marked M in the usual place (but no F or M) and then ejection port marked MMA.
Here's the upper:

That is really interesting because in the images I can find of Colts, some of that area seems to have more material than others.

You're right, my Martin Marietta Colt forging looks a bit different to Dex's Colt forging. The right side of his receiver boss looks sharper than mine, but maybe just because his is less worn. His is also not marked MMA in the left side of the pistol grip base, it looks like SL and then something else maybe. Would like to see closer pics if possible, @Dex223
Could point to a manufacturer.

I wonder if Colt/Balimoy/anybody ever used the Marietta forging in the 90's for govt contracts, or if this was some commercial-only offering. You can see this lower (and upper) is blasted similarly to Dex's receivers.

More pics for reference:















One final note, I think this upper would have gone to FN if not commercial use (and I don't ever recall seeing commercial M forge A2 uppers), since FM uppers appeared with stamped F and raised forge mark M, as seen here from a current GB auction:



The C M marked A2 uppers are all raised forge marks from my experience, this is my first encounter with an F M marked A2 upper but it proves stamped F and raised M was possible, so I attribute my 0% upper to that path.

The left side of my forging only has 7075, but it's upside down, and no MMA or other markings. (I'll dig it out and post a closer photo soon)  Great find on your upper and lower forgings!

Bumping this informative thread with another lucky find: some Kaiser A2 0% lowers. As pictured in Dex's OP but hopefully these are a bit bigger. See pics.
Markings: "KAO-11" over "8621" on pistol grip mount, level and not tilted.

Also, these all have "1027" in ink on the top, but this could just be from the shop I bought them at. Also note the smoothness of the features, less sharp than the later Anchor Harvey forgings. Also much more flash all around the forging than on the AH's.

@mb44kr

I finally took some more photos of the grip area of my Colt foging.

Left side has part of lettering ground off.  The rest is the material type.

And, again the Right side.

All of my Kaiser forgings also have inked numbers on the top as well.  3 of the 4 have 1031, the 4th has 1027.

Thanks @Dex223
Great pics & all the details. Aside from markings, you can tell our two early Colt type 3 forgings are different based on the roundness of the selector bumps. Yours are as round as the Kaiser lower forgings, whereas mine on the Martin Marietta lower were more square like the current Anchor Harvey lowers. I'm going to look through pics of early Colt lowers to see if either is more prominent or if both are even seen at all.

And my bad, I didn't realize it but some of my Kaiser lowers also say 1031. But the only numbers are 1027 or 1031 for me. That's a mystery to me, whether shop or forge did it.

It's hard to tell, but...
This one appears to have the "square" stops.


And, this one. the "round"stops.

Yes, I see! The square stops seem to have less representation online, as I could only find one example (aside from yours) with squarish stops. All the rest were round. I think aside from bothering the hell out of Kaiser or Martin Marietta/Eagle/older aluminum forging places, we've found as much as we can. Hopefully not though! I will update as I find out more, but many thanks again Dex.

The one squarish one I found (Gunsamerica):


Rounds (just links because there are too many):
https://i.imgur.com/Q7e4xsN.jpg
https://www.ar15.com/media/mediaFiles/27888/Colt_M16A2_6186016_Receiver_Left_jpg-1454034.JPG
https://www.ar15.com/media/mediaFiles/27888/Colt_M16A2_6497967_Receiver_Left_jpg-1454049.JPG
http://i1228.photobucket.com/albums/ee447/edwarde1992/20180410_182422_zpsfwmfwvmj.jpg

@mb44kar



Apparently, Balimoy used a Colt-type forging, but I believe it's a Type 2, not a Type 3 like ours.  If it's a Marietta forging, I don't know.  (It does have the more "square-ish" selector stops)

This photo is from an internet search

These two photos are from THIS site from about six years ago.  Some lucky guy found this pair of unfinished receivers (maybe BLEMS) at a garage sale. The home owner at one time worked for FN.  Both upper and lower are Kaiser Aluminum forgings.  The lower is an early variation, it has a flat spot where the mag fences meet.

I've seen one or two of those. My point was asking if all Balimoy receivers are type 2s...All I've seen are type 2 though, and we likely won't ever know. It's even cooler to think that for a short time, there were M16A1s parading around with this very A2-looking forging.


At a garage sale? Ridiculous. Those stampings are the major point of value there...Who else can say "these markings were done by FN themselves" on their clone?
Nice FK upper too, but I can't tell if stamped or raised forge mark. It's most interesting to see the milling stages FN used on lowers. These 0%'s get their pivot/takedown pin spots milled flat, and the bolt catch milled out first.

What about the front pivot pin lug variations?
my commercial (Match Target) Colt made in 2000 came with this one (pic is not mine).. seems like a transition from older A1 and the fully reinforced A2/A4 and its similar to the Balimoy 3 posts above mine

That "transitional" front lug was used on Colt Type 1 & 2 forgings.  (See Augee's Variations post)  No other forging that I know of has that lug shape.  It was used from the mid 80's until about the mid 90's.

Every photo of a Balimoy lower I have ever seen has been a Type 1 or 2 forging. (hard to tell because almost no one photos the Right side)  Also, I have never seen a photo of one that had not been restamped to "A2", and with the "AUTO" not changed to "BURST".

There are however, photos of late commercial or export A1s with A2 forging receivers.



These aren't 0% forgings.  They're just unfinished, or BLEMs.  There are more photos:

@Dex223
Even more interesting then! They mill the pocket before any drilling for the pins or selector. Also beginnings of a magwell milling. Lastly and most notably for me, it confirms that some FK uppers in military service came with the front pivot pin lug left without an inward taper at the bottom. I've seen some FK uppers with the usual inward taper on both sides, and some without. I doubt the occurrence of the taper specifies whether it is military or civilian, but we now know that both variations appear in military service.

Here are some pics I got at a gunshow today detailing some commercial 90's lowers which have both the Kaiser forging and the Colt type 3 forging. Just wanted to document the occurrence of these forgings in civilian use. Mostly Olympic arms. Interestingly, the PWA lower was both a Kaiser lower and had a (thin) FK forge mark upper.

@mb44kar



Don't be too quick to jump to conclusions.  There is nothing to say that these two pieces are a set.  They are just unfinished parts from a former employee.  Unfinished is very important here.  The tapers on the front lug of the upper could be one of the machining steps yet to be done.  I can see at least one other machining step missing on the upper.  Also, around the time these parts were produced, FN was only filling government contracts.  So, there would have been no commercial sales.



Nice photos of some old lowers.  Without seeing the full serial numbers, the Kaiser forging was produced sometime between Apr. 1991 and Jan. 1992, and the "Colt" forging between Aug. 1987 and Nov. 1989.

Kaiser forgings were definitely in civilian use.  I have three from the nineties (95 PWA, 96 Bushmaster, 98 Olympic).



I have NEVER seen a Colt forging on anything other than Colt, and ArmaLite commercial rifles.  That Olympic was very interesting.

Too true Dex, my apologies as I assumed they were both a set and that the upper was finished the milling process.

As for the Olympic lower, that is the 2nd or 3rd Olympic lower I've seen that uses the organic "Colt" forging.

I still have it hanging on the wall.......

Does anyone know which type of forging was used during the late 2000s? Particularly for a FN M16A4 made in 09. I apologize if this is beyond the time frame, but this seemed like the most appropriate place to ask. Thanks!

I apologize, I saw your post and realized I never replied to your IM. I was trying to do a little research and got sidetracked by something else. It's hard to narrow down without serial numbers to match photos, but personally, I think it's likely that the Cerro "Colt Type 5" or "Late" receiver, as mentioned above, was used in that timeframe. I've found several examples of that style of forging on A4s in photos with Marines in MARPAT and Soldiers in ACU pattern uniforms that were typical of the late 2000s (Army ACU showed up in mid-2005 in deploying units), like these two. The first one shows an FN Cerro upper, but I can't make out a forge mark in the second photo:

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Late FN A4s used the heavier tapered rear collar reinforcement that is seen on FN M4A1s as well, which appears to match the current production Cerro lower, but without the sharp point at the bottom of the magwell fence (really wish Cerro would change that back to the traditional magwell fence so we could clone some of these). This one appears to be in the 1037XXXX range:

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This serial number is 10626542, if I'm reading it correctly:

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Hope that helps!

No problem at all! I figured it was one of the Cerro lowers since my upper has a Cerro forge mark, but wasn't completely sure which. I appreciate the information!

I'm not sure if we went over this on the early "Colt" forgings, but another difference can be seen in how much the detent tube disappears in the reinforcement on the right side:

These are awesome pics! Looks like FNH is using these style lowers now. Does anyone know if colt is (or ever has in the past) used the new cerro forgings that look like this as well? If so, what were they used on?

New style cerros I'm referencing:

https://www.righttobear.com/cerro-forge-raw-80-percent-lower-receiver-p/80raw-1.htm