Hey guys what kind of barrel would you have originally found in a late GM Hydra-Matic Mod 603 M16A1 Rifle from 1969 to 1971?

Would it still have had the upside down MP marked barrel on the left side between the FSB legs?  Or would it have had a C MP C marked barrel?

I just picked up the following combo upper last week and got a really good price on it!  I originally thought it was a colt upper with a C MP C barrel but upon close inspection it does NOT have the Colt proof/inspector marks and it does NOT have any forge flashing present... so my assumption based upon this criteria makes it a GM Hydra-Matic Upper Receiver.  Also included with this upper was an unmarked later Vietnam era Bolt Carrier and an unmarked Bolt.  It also has a C MP C near mint barrel in it with the forge flashing milled off of the FSB.

Here is the link to the auction...

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=489035131

Any help you guys might offer would be appreciated because I would like to build this rifle right!

Brandon

Nice score!!!!!

Based on the limited pictures and rebated front lug I'd say Colt replacement parts upper if no actual proofs.  Sometimes proofs are very lighly struck but I've had a few very similar upper receivers over the years with a mix of barrels that were arsenal built and not factory assembled ( no proofs).  Very nice score regardless for a very decent price based on condition I'm seeing..  XM16E1 upper receiver would be great foundation for various pre 1970 builds..

http://www.ar15.com/forums/t_3_123/584919_GM_or_HandR_upper_assembly__an_old_and_somewhat_confusing_subject_.html

The first C in "CMPC" stood for "colt", so it obviously wouldnt be correct for a GM or HR build.