you don't know if the 2 gouges on the bullet are from the mag feed lips, or from the M4 feed ramps of the barrel extension.
Metal mag feed lips carve out gouges on the brass, not so much the bullet projectile.
you probably have some serious sharp edges on the barrel extension feed ramps, left over from the usual machining. This is common with most AR barrels. Those sharp edges can be deburred and polished so you don't get gouges on the projectile, but that usually has to be done before the barrel is assembled to the upper. That extra-special romancing of these particular machining edges is not normally performed by AR gun manufacturers or barrel manufacturers, but usually the domain of AR gun enthusiasts who lovingly and painstakingly assemble their uppers with a critical eye to all sharp edges. It adds a sh!t-load of time to the assembly process, therefore not included with AR gun manufacturers. I'm not sure if even the $1,000 AR barrels include that extra touch. I use some round, half-round, and triangular 1/4" stone hand-files, followed up by polishing with a dremel felt cone. Do not use a dremel rotary stone because you will instantly F-up the barrel feed ramp geometry (just my opinion).
The Other Site: how to romance your AR
I'd guess that after 500 to 1,000 rounds of shooting, those sharp edges may just get "deburred" from normal usage. plus-or-minus. copper & brass wearing on steel.
