View Full Version : Barrel Extension and Upper fit

John Hwang
26 September 2012, 10:49
We get this question asked a lot so I'd thought I'd post a picture provided by AR15Barrels.com. The key is as the bullet is traveling up from the magazine, you don't want it to hang. Even in this picture where the M4 extension and upper receiver meet (top right), you can see where the bullet can hang. You can take a small file or dremel (very carefully) to make that area perfect.