This customer had an older model that used shorter nipples than the standard. We sent him a set of our Pocket model nipples and those fit correctly.
This is an easy fix. The problem is with the gun, not the nipples. Take it to a competent Gunsmith that knows black powder revolvers. Your timing is either off or tolerances are out of spec. It could also be that the notch in the hammer has a bur on it causing this problem.
We clearly list the recommended caps to be used with our nipples. This is provided on our product page, FAQ page and on the product packaging itself. Nowhere does it show CCI #10’s to be used. CCI #10 caps have a much smaller inside diameter and will not fit correctly.
These products are recommended with items in your cart.