Use a bore scope after cleaning with attention to the neck area in the chamber. If there is a gremlin there, careful polishing can sometimes fix it.
Note that the case neck expands after firing and can encounter sharp edges on the way out as the ejector pushes it to one side.
Look for brass color at the sharp spots on the feed ramp edges or elsewhere in the barrel extension.
Note that the case neck expands after firing and can encounter sharp edges on the way out as the ejector pushes it to one side.
Look for brass color at the sharp spots on the feed ramp edges or elsewhere in the barrel extension.