I have this upper with no markings at all on the receiver. The barrel, front sight post, and bcg are all colt. The barrel is marked c mp b. The front of the receiver does not have any flash. Value?

Maybe H&R or GM.  I suck on the non-colts.  If it is either, I would say $700-$800, as they are scarcer than others.  It could also be a PWA or SGW A1 upper with a GI barrel.  I don't remember what forge codes they used.  Hopefully the smarter than me people here will chime in.

BTW, that screams for a NDS black anodized A1/603 lower!

I was thinking H&R or GM. I've tried to research it the best I can, but still unsure. Thanks for your response.

Hello, thanks for posting this.  I don't think we know everything about the non-Colt uppers so every chance to see pictures of more examples helps.  Some questions:

If there is no forging flash on the front, are there tool marks that run from side to side?
Is there a small circular depression with a raised number cast in the back of the forward assist?
For the BCG, "C" stamped on the left side?  Any markings on the bolt?  (MP marked bolts have many variations, pictures help)
Does the charging handle have a row (sometimes 2 rows) of square depressions in the back?  Many have a small flat spot pressed / ground in the right side "T".

Thanks for posting, more pictures would be nice to see.  One other thing to pay attention to, are there any signs of paint chipping?  Some parts were painted / refurbished and you can sometimes see chips / wear areas where parts contact each other.

There are tool marks going side to side on the front.
Didn't see anything on the forward assist.
The bolt carrier has the C on the left side and bolt is marked MPC.
Didn't see anything on the charging handle like you described.

The only thing that appears to be painted is the charging handle. It's black.

What would you like pics of? Will try to get more pics tomorrow.

aren't stripped parts kits (minus the barrel) getting close to this in price? used sp1 barrels are going for more than $200 anytime i see them anymore.

i miss $400 complete 603 "upper halves".

I ended up selling it to a dealer today at the Knob Creek machine gun shoot for 700.

You probably did OK.

GM upper with a Colt barrel.

Thanks for posting those, it is always nice to see more examples.

Yep!!