Authentic USGI M16A1 Parts?

Got the itch to build a retro clone, so I bought the parts, and then an offer came up for another receiver, two bolts, and a charging handle that I couldn't pass up. Just wanted to verify that these are USGI M16A1 parts! Thanks!

BCG's marked with "C" and seemed to be parked:
Attachment 68835
Attachment 68836
Attachment 68837

Charging handle no markings:
Attachment 68838

SP1 upper, lightly parked, has what seems to be triangle markings near barrel attachment area but I can't make out what they are:
Attachment 68839
Attachment 68840
Attachment 68841

The C on the carrier is Colt, your upper may also be Colt

I will try and find a photo of a Colt upperAttachment 68850


found a Colt 606 upper photo

Colt SP1 upper will have C M in the recess under the rear sight (right side).

Neal

Quote:

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Originally Posted by Neal Myers

Colt SP1 upper will have C M in the recess under the rear sight (right side).

Neal

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Not necessarily. Those are forge marks and there could be a variety of companies making them. Mine says CH
Some earlier uppers had no marks at all.

To the OP.
The triangle over the square box at the front of the upper looks to be the colt verified proof over the c in box inspectors stamp, which would mean that upper left colt assembled as a rifle and test fired.
I vote it's an original A1 colt upper and not sp1 if both attach lug holes are the same size.

https://www.ar15.com/mobile/topic.html?b=3&f=123&t=401263

Quote:

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Originally Posted by wbaad

Not necessarily. Those are forge marks and there could be a variety of companies making them. Mine says CH
Some earlier uppers had no marks at all.

To the OP.
The triangle over the square box at the front of the upper looks to be the colt verified proof over the c in box inspectors stamp, which would mean that upper left colt assembled as a rifle and test fired.
I vote it's an original A1 colt upper and not sp1 if both attach lug holes are the same size.

USGI Colt 603 XM16E1/M16A1 upper buyers guide Edition II -

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So I just got home and the front lug hole is closer to 3/8" from inside to inside. My standard m16A1 upper is close to 1/4" inside to inside. I placed a USGI front lug pin inside to show difference. So I'm assuming that makes this an SP1, however I'm confused because the rear site markings are consistent with a 604.

Attachment 69054
Attachment 69055

Yup, that's the big hole, for the transverse screw.

There is an adapter out there that someone sells. I can't remember who had them but essentially it is made to take up the room of the large pivot and align the upper and lower.

ETA:
https://www.milsurps.com/images/impo...oltbushc-1.jpg
DPMS Offset Pivot Pin Adapter Bushing .315 to .250 Diameter AR-15

Yes, before these were available, I made one. It worked ok for just shooting, mating the parts together. When you drop the top forward to remove the bolt, then try to close it up again, you may well have trouble making them go together properly. It may move out of location. Better than nothing I guess.

If I decide to keep the SP1 upper, I will just order the correct style lower from NODAK, along with their pin. Thanks for the help guys! If anyone has any leads on 601/602/604 uppers, let me know!

Related question to early M16 series, when did the US built rifles start getting staked gas keys?

The reason I ask, is the the process came around in the Canadian rifles only somewhat recently. When I was awaiting course loading at CFB Wainwright in 2003, I ended up tasked out to the Training Stores and weapons vault. One of my duties was to physically inspect each of their 2500 C7A1 bolts and separate any that did not have the key staked in and a single "punch mark" on the top to signify the modification had been completed. It was a tedious task that took longer than a guy would think, several days for 8 hours a day, nothing but bolt sorting.

The Canadian Army, making soldiers hate firearms through overexposure since 1867. LOl!

SP1 Uppers are perfect for 601 or 602 builds!

Darren, I'm guessing but I'd say gas key staking was in place by the mid-late 1960's. The problem of loose gas keys would have been addressed early on during the fielding of the M16 in the Vietnam conflict and subsequent product improvements that came later as these problems were all discovered. There have been countless improvements to the AR platform in it's almost 60 years of service. They are near flawless now for function. A testament to an excellent design that like all machinery, got needed improvements as necessary over the course of it's service life.

Interesting, perhaps Diemaco (Now Colt Canada) didn't get the memo, or maybe we had a batch that the staking was missed.

I agree about the excellent design, before being a soldier I had the "textbook" opinion about them, underpowered plastic poodle shooters that weren't a "real" rifle.

After using them professionally and personally for over 17 years I appreciate the ergonomics, reliability, flexibility and modularity of the rifle. I certainly never felt undergunned.

Take 10 rifles, strip them to their last spring and screw, throw them in a pile, and reassemble 10 rifles without any handfitting, like assembling Lego.

In service we didn't even serial the bolts to rifles, we tried to keep them together in stores, but often things got mixed up, regardless, they just worked.

In fact whenever I handle a new production semi-auto design, I always hold it to the AR-15 platform standard for ergonomics and function. So far, I have not encountered a firearm that I believe "does it better" Some have come close, like the Robarms XCR series, but that unnecessary AK gas system throws the balance forward, and having a piston rocking about upsets the otherwise smooth shooting cartridge.

I quite like the AR15 platform, always will likely.

It is kind of remarkable that 54 years after first combat use, and 52 years after first adoption by the US army, it is still the first line rifle for the US and Canadian armies.

You have to go back to the Brown Bess/1777 Charliville muskets to get to arms that has such a long first line use in the US army/pre army.