colt barrel question

[chuckman]

I have a barrel marked C MP NATO 5.56 1/7. Now, I know what all of that means. But near the upper receiver and just barely under the gas tube there is a stamped C (O?). Does this refer to chrome-lined chamber and barrel, or just chrome-lined chamber? I presume since it's a Colt barrel it's good to go until I shoot it out. FWIW I used the search function and came away with some ambiguity....maybe because it's early and I am undercaffeinated.

[Iraqgunz]

It's some kind of code and nothing you need worry about. Bottom line is that the barrel has a chrome lined chamber and bore. This is standard for almost all Colt barrels.


I have a barrel marked C MP NATO 5.56 1/7. Now, I know what all of that means. But near the upper receiver and just barely under the gas tube there is a stamped C (O?). Does this refer to chrome-lined chamber and barrel, or just chrome-lined chamber? I presume since it's a Colt barrel it's good to go until I shoot it out. FWIW I used the search function and came away with some ambiguity....maybe because it's early and I am undercaffeinated.

[5pins]

The “C” means it’s chrome lined, the “MP” means it’s magnetic particle inspected, “NATO 5.56” means it’s chambered for the 5.56mm cartridge, and the “1/7” means it has a one in seven twist rifling.

[chuckman]

Thanks. I know there are a butt-load of barrel markings; just curious as to what I have.

[Iraqgunz]

I think he is referring to the C or O looking that is near the rear of the barrel (by the upper receiver).


The “C” means it’s chrome lined, the “MP” means it’s magnetic particle inspected, “NATO 5.56” means it’s chambered for the 5.56mm cartridge, and the “1/7” means it has a one in seven twist rifling.

[5pins]

Wow, I completely miss read his post.

Maybe I was undercaffeninated.

[Split66]

They could be quality control marks. I've heard somewhere they will stamp the barrels like that after they've passed all the tests as an overall final "colt quality" marking.