I have had the same problem the last 2 years. I bought 1000 cans of #11 caps and 2 of the 10 cans were very tight and didn't fit on the nipple. Some caps didn't fire because of the tight fit and the ones that did fire I had one heck of a time getting the spent cap off. To me, it's a Quality control problem. I have less problems with my Flintlocks.