I had that happen once , I found out that I had a shell holder that was was short and caused a head space problem when I full length resized my brass. The shell holder and a bunch of brass went in the garbage and the problem went away.
That almost happened to me. I inherited a bunch of equipment from my brother. Among it was a shellholder he had ground down for some reason. Fortunately, I ran the cases through a gauge before loading and shooting them. Also fortunate us that they were from a mixed group of once-fired Feds from my big stash of .270 brass and not new cases.
