Hi Guys -- For my first post, I've got a Q about the A-1 style barrelled uppers I'm seeing. I know a lot of 'em are Colt take off's with a standard A-1 style upper With the colt large holes. What are the A-1 uppers with the A-2 shell deflector cast in? Just picked one up with small holes (to mate with the lower) light bbl, and fwd assist. Under the rear sight on the C handle, the letters -- D , K, are cast in, and  the bbl is stamped  -- c mp b. Mine cost me 225 and will work great for my not quite authentic A-1 forgery. Since I'm left handed I'll take the trade off with the cast in shell deflector. Plus I saved 100 over a colt large hole version, that I saw today.  Where do these things come from? Thanks

I do not know about the markings. Bushmaster has a lot of A-1 sight, built in deflecter, small pin uppers out there.  My favorite btw.

The A1 sight, shell deflector equipped upper was created essentially for the Canadian M16, the C7. The Canadians didn't want the A2 sights on their version. Colt did sell some AR15s with this type upper as well.

Given that the markings on your barrel (C MP B) indicate an early, fully chrome lined piece, I would suspect that it's an aftermarket put together; since the upper would have been made several years after the barrel.  Later chromed A1 barrels are actually marked "chrome bore".

The D  K markings I'm not positive about.  "K" should be Kaiser, as producer of the raw forging, but a Colt piece should be marked "C   K".  The "D" may stand for "Diemaco", the Canadian outfit that makes the C7.  Currently, Diemaco uses their corporate emblem as an ID mark, but perhaps they used the "D" on early production pieces.

BTW, though you use the word "cast" in you note, be aware that nothing on your piece is a casting.  All strictly forgings

The "DK" marked C7 uppers have been kind of a mystery. I've had two, sold one, and CMMG had a used one for sale awhile back. Diemaco uses a very stylised "D", that is different from from these uppers. Both of mine came with cheap chromoly barrels that used roll pins for the FSB, it sounds like yours has a nice Colt barrel on it.

Thanks for all the info. The upper assembly cleaned up really nice. Can't wait until Sept. to put this thing on a lower.