I'm 55 years old and have been reloading since I was 13 years old. Except for a few Winchester primers on occasion, I have always used CCI primers, mostly CCI 200 large rifle. I had never had any problem whatsoever until I used Lot No. C01L in my 7.5 Swiss.
I had already shot over 2,000 rounds loaded with other lots of CCI 200 primers when suddenly, in more than one of my K-31 rifles, I got what I call milisecond hangfires. You feel the firing pin hit, but there is this milisecond delay in ignition. It was a weird feeling, but they none completely misfired.
I traced the problem to the new 1,000 primer box of CCI 200s that I was in the middle of using (Lot No. C01L) (I have over 6,000 CCI primers in stock of other lots, thank goodness). I called and spoke with the technical guy at CCI. He was very pleasant, but in a very polite way kept implying that it was a problem with my seating of the prmers. Essentially, he felt they were just a tiny bit shy of bottoming out and the initial strike of the firing pin was completing the seating before ignition.
Okay, it made some since except for the following:
1. I was using (and I'm still using) the same batch of cases that had fired prefectly with other lots of CCI 200 primers 15 times before and fired prefectly over 7 times since. And yes, I anneal my brass and take good care of it...it's Norma and expensive.
2. I was using the same hand priming tool as the previous 2,000 reloads of 7.5 Swiss.
3. Both rifles that were having the problem had each fired over 500 reloads with CCI 200 primers before with no problem.
4. As soon as I opened up another lot of CCI 200 primers (Lot No. J12L) and began reloading using my same equipment, loading technique and firearms, everything starting firing great again (and has been for almost 1,000 rounds).
So, if someone who goes to Angeles Shooting Range in the Los Angeles area on Saturdays wants the remaining 500 CCI primers of Lot No. C01L for free to experiment with, they're yours. As for me, I simply threw them in a corner and had forgotten about them until I read this thread.
I think one of the problems is they don't want to pay the hazmat fee to get the primers back and ship replacements. That would be like a $50 saddle on a $5 horse. So, they live in denial. Of course, I'm sure they get their share of calls from Yahoos, too.
FWIW