Honed uppers

[Bullit Bill]

Hi, everyone. I just bought a Rock River F/T upper and lower to start my first AR build, and noticed the bolt carrier bore had been honed, not just reamed like I had assumed it was. It has an actual cross-hatch pattern and of course is extremly smooth, which is what made me give it a closer looksee after I felt it. Is this common amongst most manufacuers? I was just curious more than anything.
Thanks, Bill

[Colorado Osprey]

Most carriers including RRA are made by CMT. The exception is Olypmic Arms who make their own. Both CMT and OLY finish hone the inside of the carrier for the bolt gas rings to make an air tight seal. With out honing it would tear up the gas rings and would fail to function in short order.

The only manufacturer carriers I'm not sure of is rifles made for Colt by FN. I think they are CMT also, but not 100% positive.

[Bullit Bill]

What I ment was the channel in the upper recever that the bolt carrier slides back and forth in. After re-reading my post I relize I made it sound like the bolt bore in the carrier :roll: Thanks for responding, Colorado Osprey.