Authentic USGI M16A1 Parts?

[garrettbragg12]

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

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[RCS]

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

[Neal Myers]

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

Neal

[wbaad]

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

Neal

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

[garrettbragg12]

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 -

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

[browningautorifle]

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

[Bill Hollinger]

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:

DPMS Offset Pivot Pin Adapter Bushing .315 to .250 Diameter AR-15

[browningautorifle]

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.

[garrettbragg12]

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!

[Sentryduty]

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!