Had the same problem with a brand new Crocket .32 years ago. Solved it with a little washer under the nipple (actually used a washer made to back up a pop rivet behind sheet metal - I drilled it out so it would fit over the nipple threads). It raised the nipple enough so the caps would fire. I also had a problem with #11 caps being too loose on my .44 revolver. A box of #10 caps solved that.