Barrel Question

[jpprescott]

I just picked up a Colt M4 upper in a trade. The upper reciever is correct (marked C AF), but I have questions about the bbl and FSB.

The barrel is marked: C MP 5.56 NATO 1/9
FSB is marked: G7 I 1 (no F that I can see)

Can anyone tell me what I have here?

J. Prescott

[Robb Jensen]

I just picked up a Colt M4 upper in a trade. The upper reciever is correct (marked C AF), but I have questions about the bbl and FSB.

The barrel is marked: C MP 5.56 NATO 1/9
FSB is marked: G7 I 1 (no F that I can see)

Can anyone tell me what I have here?

J. Prescott

It's a Colt chrome lined barrel with a 5.56mm NATO chamber with 1/9 twist. The FSB appears to not be a F height one so if using with a flat top upper receiver so you may have zeroing problems and may need a taller front sight post.

I commonly see Colt barrels with those markings/FSB & twist on their 6520 rifles, these are (.625" profile) which is the what Bushmaster replicates with their Superlight barrels.

[jpprescott]

Thanks GotM4,

The barrel is M4 profile with M4 feedramps though.
I didnt know that Colt used 1/9 on an m4. Is it possible that its not a colt barrel?

J.Prescott

[Robb Jensen]

Thanks GotM4,

The barrel is M4 profile with M4 feedramps though.
I didnt know that Colt used 1/9 on an m4. Is it possible that its not a colt barrel?

J.Prescott

C MP marking is indicative that it's a Colt barrel. They do use both 1x7 and 1x9 on certain models.

[jpprescott]

Thank You.

J.Prescott

[ls6man]

The Colt 1/9 twist barrel M4 profile was used on the Colt 6922, which is the same rifle as a 6920 except for twist rate.

Here is a few pics of my rifle.

http://i147.photobucket.com/albums/r306/ls6man/100_2021.jpg

http://i147.photobucket.com/albums/r306/ls6man/100_2024.jpg

http://i147.photobucket.com/albums/r306/ls6man/100_2022.jpg