Solution for dented case necks?

[SG4247]

What I call the "vampire effect" on the case necks comes from when the spent case is extracted from the chamber, and the ejector forces the case out of line with the bore once it clears the chamber, hitting the lead edges of the barrel extension teeth in the ejection clock position.

Klem and LR are 100% correct in this. Some manufactures of barrel extensions and good gunsmiths will cut a small chamfer on the barrel extension lugs, in the lathe, from the barrel side. This is done before the extension is screwed onto the barrel threads and locked in place.

This actually accomplishes two things:
1. Keeps vampire tracks off your case necks.
2. Provides extra clearance to for the radius on the back side of the BOLT lugs. Hopefully your bolt lugs have a slight radius on the root to prevent cracks from forming. If the radius on the bolt lugs is too large, there could be interference with the extension lugs and headspace will be inconsistent - and bad things could result.

Ask your smith to check for or add the chamfer if you ever have a custom AR barrel made.