Well, knock on wood (my head) but I haven't really had a problem with cap fragments. I'vd had fragments fly off just like everyone has but I haven't had an action hang up. I thought I was going to one time for sure on the little '49 because I didn't see the spent cap after I had shot a squirrel, but it had fallen completely off onto the ground. Most of the time, at least for the most part, my cap's stay on and when I look at them they have burst into sort of a star shaped pattern.
I looked at an original LeMat one time year's ago at an antique shop down in the French Quarter in New Orleans. (not too many year's ago. I was still in the Merchant Marines then [that was after I was through with the Marine Corps] and the ship just happened to dock there) That LeMat had the biggest nipples on it I have ever seen on a blackpowder gun. I don't know what size they were but they were huge....