Need help identifying upper

[dentron]

I just picked up this upper reciever and would like to know more about it. From the research I have done, I believe it to be a 603 or 604 model. It has C M forge code and the barrel is marked C MP CHROME BORE. It does not have a forward assist. I think it has a larger diameter front pivot pin hole. Square C proof mark, no marks on FSB. Does have dust cover. Has bird cage FH.

Any info would be great.

Pictures:
http://uploads.tapatalk-cdn.com/20160120/73f5c637946e8a23fece91cdf020f7a8.jpghttp://uploads.tapatalk-cdn.com/20160120/1f908e77c58b7e50b4c2bca96713fb5b.jpghttp://uploads.tapatalk-cdn.com/20160120/0032dc969c744cafd1b98830d6b8e0af.jpghttp://uploads.tapatalk-cdn.com/20160120/00c8d5087d4b8d3660e640383622d545.jpg

[herd118]

It's a Colt SP1 (semi-auto,commercial) upper.

[mack7.62]

Also know as a big hole due to the pivot pin being larger than normal, use on a standard sized lower will require an adapter.

[Renegade04]

What you have is an Colt SP1 upper assembly. Not a 604. The 604 uppers did not have the .315 hole for the pivot pin. Only the SP1 uppers did. 603 uppers have forward assist. I have the exact same upper assembly on my 1977 SP1. The C MP CHROME BORE barrels were used starting in 1974. M16A1s used the same barrel up until production ceased (around 1982). The C M forge code is for "Colt / Martin Marietta".

[dentron]

Ok, thank you for the clarification. I will source an adapter and clean this thing up.

[Renegade04]

Ok, thank you for the clarification. I will source an adapter and clean this thing up.

http://www.midwayusa.com/Product/599768/dpms-offset-pivot-pin-adapter-bushing-315-to-250-diameter-ar-15-matte

[dentron]

http://www.midwayusa.com/Product/599768/dpms-offset-pivot-pin-adapter-bushing-315-to-250-diameter-ar-15-matte
Discontinued, but thanks anyway. I found some at fulton armory and jse surplus.

[Renegade04]

Discontinued, but thanks anyway. I found some at fulton armory and jse surplus.

Sorry. Missed that part.