This is my first build and found this candidate. The upper I got at a local gunshow. Its a mid '70's vintage A1. The B/BC is a spare. The gas key is pretty worn and the bolt has some markings that I haven't been able to decipher. It looks like a P in a circle and an M in a circle. Any ideas?
http://i104.photobucket.com/albums/m177/1Raider75/M16pics001.jpg
http://i104.photobucket.com/albums/m177/1Raider75/M16pics002.jpg
http://i104.photobucket.com/albums/m177/1Raider75/M16pics003.jpg
http://i104.photobucket.com/albums/m177/1Raider75/M16pics004.jpg

To hell with the bolt. tell us about the H&R M16 lower..

I got the lower from CMMG. It's a Stemple redo. Paperwork from ATF was a snap and was returned super quick. Funny thing is that it is registered as being made by H&R and not Stemple. I am going to send it off to US Anodizing to get refinished as it is too dark for my upper and whatever finish is on there is chipping off. Once I get it back I'll post some pics of the whole enchilada.

It looks like a P in a circle and an M in a circle. Any ideas?

Early hard-chrome-plated bolt acid-etched with M & P, signifying the bolt has been Magnetic particle inspected and Proof tested.

Thanks, Dump. That makes sense. All I need now is a decent Safety Selector that doesn't have the ambi markings.

Quoted: Thanks, Dump. That makes sense. All I need now is a decent Safety Selector that doesn't have the ambi markings.

I just saw a ton of those at the gun show.  Don't know the quality.

Hi Tman,
    Post pics of the disassembled bolt and carrier showing the extractor spring (& insert if it has one), any markings (like "C") on the left side of the carrier, and staking on the carrier key. This will yield better info on the B&C group in your Colt Harvey upper.
    Stemple was very creative in putting his ATF required info on his rewelds: under the grip, inside the mag well, etc. He preferred to reweld H&R M16 receivers, but did a few Colts as well. Never seen a Stemple rewelded Hydromatic, but he probably did those also. Do a FOIA on your NFA receiver for complete info. Where did he mark yours?
                                                  Thanks,
                                                  Carey (Kingwood, TX)

Carey,
Here are some pics. The bolt is not marked.
http://i104.photobucket.com/albums/m177/1Raider75/TSMGpics002.jpg
The extractor has no insert (little rubber thingy) in it.
http://i104.photobucket.com/albums/m177/1Raider75/TSMGpics009.jpg
The carrier key has two square stakes.
http://i104.photobucket.com/albums/m177/1Raider75/TSMGpics008.jpg
I wont be using this one as it is a spare and the bolt lugs are kinda worn on the edges and the carrier key has a mild bell shape to it.

The staking for the key on the bolt carrier makes me think that part is Colt.

Quoted: Carey, Here are some pics. The bolt is not marked. i104.photobucket.com/albums/m177/1Raider75/TSMGpics002.jpg The extractor has no insert (little rubber thingy) in it. i104.photobucket.com/albums/m177/1Raider75/TSMGpics009.jpg The carrier key has two square stakes. i104.photobucket.com/albums/m177/1Raider75/TSMGpics008.jpg I wont be using this one as it is a spare and the bolt lugs are kinda worn on the edges and the carrier key has a mild bell shape to it.