I had a Pietta 1858 Remington that wouldn't take #10 caps no matter what. It must have come with #11 nipples instead of 10. It liked Remington #11's plenty though.
I personally prefer Remington caps to CCI's across the board for exactly the reason that was happening to the OP. Even on #10 nipples the #11 Remmies work good for me if I pinch the cap a bit.