I had the same kind of problem with shells from a well-known manufacturer of 2.5 inch shells. This has only happened with one box of shells. Learned they get their hulls, primed, direct from Cheddite. Turned out, about 1/3 in that box had primers set about .010 too deep. Discovering this took a steel rule and a bright light. The deep-set primers were getting strikes too light to set off the primer. I set the ones with the deep primers aside. I guess even a good manufacturer's machines get a skosh out of adjustment from time to time.
Grateful for the tiny-rubber-band solution, I will try that with the deep-set primers.
