I just bought an upper thru the EE. I wasn't sure just what I was getting, but the price was right (the seller wasn't sure just what he had either).
What I've got is a brand new, unfired upper, complete except for bolt/carrier group (it includes the  charge handle, which has no wear marks on it whatsoever.
The upper receiver is an A1, marked with a "C" and an "M" in the recessed space below the sight adjuster. It has no forward assist, nor does it have a shell deflector. It has a large pivot pin.
The barrel is 20", with triangular handguards. It is marked "C MP CHROME BORE" on top just behind the flash suppressor, which has 6 eually spaced slots (birdcage?).
The FSB has a sling swivel and bayonet lug, and is marked "C" just below the sight.

Can someone give me a positive ID on this upper? Thanks for any input.

Quoted: I just bought an upper thru the EE. I wasn't sure just what I was getting, but the price was right (the seller wasn't sure just what he had either). What I've got is a brand new, unfired upper, complete except for bolt/carrier group (it includes the CH, with no wear marks on it whatsoever. The upper receiver is an A1, marked with a "C" and an "M" in the recessed space below the sight adjuster. It has no forward assist. It has a large pivot pin. The barrel is 20", with triangular handguards. It is marked "C MP CHROME BORE" on top just behind the flash suppressor, which has 6 eually spaced slots (birdcage?). The FSB has a sling swivel and bayonet lug, and is marked "C" just below the sight. Can someone give me a positive ID on this upper? Thanks for any input.

The upper receiver and barrel are Colt. The CM is the forging code which means Colt and the forging vendor was Martin Marietta. The barrel has Colt proof marks on it. The bolt carrier sounds strange. If it is Colt , It should just have a "C" on the left side. I have never heard of a CH.

Quoted: Quoted: I just bought an upper thru the EE. I wasn't sure just what I was getting, but the price was right (the seller wasn't sure just what he had either). What I've got is a brand new, unfired upper, complete except for bolt/carrier group (it includes the CH, with no wear marks on it whatsoever. The upper receiver is an A1, marked with a "C" and an "M" in the recessed space below the sight adjuster. It has no forward assist. It has a large pivot pin. The barrel is 20", with triangular handguards. It is marked "C MP CHROME BORE" on top just behind the flash suppressor, which has 6 eually spaced slots (birdcage?). The FSB has a sling swivel and bayonet lug, and is marked "C" just below the sight. Can someone give me a positive ID on this upper? Thanks for any input. The upper receiver and barrel are Colt. The CM is the forging code which means Colt and the forging vendor was Martin Marietta. The barrel has Colt proof marks on it. The bolt carrier sounds strange. If it is Colt , It should just have a "C" on the left side. I have never heard of a CH.

complete except for bolt/carrier group (it includes the CH)

Charging handle/minus BCG!

Thanks a lot guys. Appreciate your input.

Two more questions:
   1. Is there any difference between an SP1 upper and an upper made for the military?

   2. To build this into a proper SP1 (or semiauto M16?) I assume I would need an A1 lower receiver. I saw in a retro thread somewhere recently where someone "converted" a current lower receiver into a retro receiver (A1? SP1?) by grinding some of the fence off and grinding down the receiver extension boss. This sounds like a lot of work, which could easily be screwed up. Is there another option? (Of course one option would be to simply use a modern Colt lower receiver, with A1 furniture, knowing that 99% of even Vietnam vets wouldn't notice the difference).

Damn!! It's amazing how fast a "current" posting can disappear into oblivion! i think I found the answer to question #1 - small pivot pin vs large pin - but I'd still love some input on  Question #2.  Can anyone give me any help on this one? Thanks!!

Quoted: Damn!! It's amazing how fast a "current" posting can disappear into oblivion! i think I found the answer to question #1 - small pivot pin vs large pin - but I'd still love some input on  Question #2.  Can anyone give me any help on this one? Thanks!!

If question #2 is where you asked if this upper could be built into an SP1, the answer is; only if you can find an SP1 lower to mount it on.

Please understand, the Colt SP1 was a one of a kind type.  The lower was totally flat sided, the rear ring is the early type, which you can't get on a factory lower any more,  and Colt only produced the thing the way they did to dump some very early lower reciever forgings that couldn't be used to make M16s, and or M16A1s because of the flat right side.

I guess, if you're a master machinist, or are willing to pay one, you could theoretically convert a current lower to SP1 profile; but why the hell would you want to?  It was a bastardized design in the first place.  To my mind you'd be much better off getting one of the reduction sleeve type adapters from Bushmaster, or whoever, and mounting the thing on a current lower.

And oh, by the way, I've been an SP1 owner since 1975

The only reason I keep the one I have now, is that I class 3d the thing in 1979, and I'm counting on it to put my 9 year old through college in 10 years or so

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