Colt Upper?

[stenz]

There is a Bushmaster XM15-ES2 that I am wanting to buy. They guy says it has a Colt Upper.

So my question is, how do I tell that its a Colt upper?

Thanks,

Jake

[BPTactical]

Well for one it won't say "Colt" anyplace on it. You are going to have to go by forge markings and even that is no sure guarantee. Colt used forgings from Cerro Forge, Martin Marietta, Alcoa to name a few. So did most manufacturers though. Do a bit of hunting online and research forge markings and you will find a wealth of information. Colt finishes vary from a dark grey (usually found on earlier models) to dark black.
I am not aware of a way to absolutely ID it as Colt.

[stenz]

There are 2 forged stamps on the upper. One is a C and the other is an AF combined in one letter so, I am pretty sure its a Colt upper.

There is also a marking on the barrel that is next to the 5.56 NATO and its says MP? Any idea what that means?

What do you think its worth? Its in great condition and comes with a YHM flash hider.

[BPTactical]

There are 2 forged stamps on the upper. One is a C and the other is an AF combined in one letter so, I am pretty sure its a Colt upper.

There is also a marking on the barrel that is next to the 5.56 NATO and its says MP? Any idea what that means?

What do you think its worth? Its in great condition and comes with a YHM flash hider.

The C marking denotes Cerro Forge IIRC. Without being at my shop I cannot verify the AF marking.
The MP on the barrel denotes Magnetic Particle inspected (Magnaflux). What is the twist rate of the barrel? Chrome bore?
Check the bolt as well. A Colt bolt will have a C stamped on it plus the MP IIRC.

For a non factory rifle it is worth the sum of the parts. Figure 5-600 for the upper and 200 for the lower. That's just me though and what I would pay.

[Graves]

A raised marking that looks like a keyhole is cerro forge, the C usually means Colt. Other Colt markings will be CAF, CH, and CM.