This article initially appeared in PS 788 (Jul 18), p. 42.
When M885A1 rounds are fired through an M249 machine gun, a small dimple is often created in the feed throat of the barrel.
It’s usually no problem. Testing has shown that even 25,000 rounds fired through a dimpled barrel caused no problems.
Dimple in feed throat usually not a problem
Barrels with a dimple are considered good to go as long as there are no extraction problems. If there is poor extracting, replace the barrel.
Also replace the barrel if there are feeding problems or the headspace gage won’t seat.