Ever happen to anyone else??? More than a "FEW" times!
Shoulder bumping and neck sizing helps to eleminate that problem. Full length resizing with the expander ball pulling the neck up will contribute to the problem.
The case gets longer as you resize, you trim to length and reload. Where did that extra length that you have to trim off come from? From the case body stretching!
The .308 isn't a lightweight! Lots of power there and the brass really gets worked. After 5 or 6 firings and full length resizing, my guess is the brass at the web area is starting to get pretty thin.
By shoulder bumping and sizing the neck, you keep your brass from growing any more than needed. As the brass starts getting snug in the chamber, you body or full length size till the bolt closes easy. Bumping the shoulder back .001 or .002 keeps the brass from growing more than needed.
(I've got BR brass with 25+ firings on it, still doesn't need trimming and it's still going strong)
And, a "Broken Case Extractor" for every caliber you shoot is something you should keep in your range bag!
Nothing worse than 1/2 a case stuck in the chamber to end you fun! Bent wires, oversize brushes, gouged chamber walls from trying to remove the broken case?
Get the proper tools and keep them with you every time you go shooting.
Try a broken case in a M1A. After it's damaged the next few rounds trying to reload, you'll figure out you've got the front half of a broken case stuck in the chamber.
The broken case extractor saves the day!!