Looking For Info on Ar15

[Mr. Booshie]

Bout tree fiddy

 

[opps]

Colt Martin Marietta M16 A1 upper, second gen barrel with chrome lined bore.

 

[jeep78]

I think it predates the A1. No forward assist.
It is an original M16

Original barrel was 1 in 14 twist. Then went to 1 in 12. Then went to 1 in 12 with chrome chamber. Then went to 1 in 12 chrome chamber and bore. Then went to......... ad infinitum