Neck of casing flat spot?

[RStewart]

My point is clear. Heavy buffers solve feeding, reliability, and brass ejecting problems which is why the military and Colt (BTW Colt is the military's biggest supplier of black guns) run "H" buffers. FN has never made 5.56 ARs only ARs in 7.62. FN 5.56 family consist on the FN CAL, M16s licensed and speced by Colt, and of course the more recent 5.56 Scar. I have no clue what you're talking about...

IMHO you're taking a simple question about a flat neck and turning it into a design/modification/buffer discussion. I can Google all kinds of stuff, too, but it don't mean it's right. We were just trying to give the guy an easy, cheap fix. Not overhaul the system.