Actually I didn't. It was much simpler than that.
I started out with a cap & ball revolver, the only caps I could find locally were #11 magnums so I used them just because they fit the nipples!
Later I got the CVA carbine & it came with some #11 non-magnums, but it had never been fired, heck it had never had the barrel fitted to the stock!
I tried the #11's & no BANG, just a *poot* so I went with the #11 Mags after that. When I tried the regular #11's on the revolver, figuring I could shoot them up on there with the shorter & more direct flame path, it was a noticeably slower ignition sequence than the magnums, but at least I can "shewt 'em up" that way!
Here's a blow up of the breech area showing a drum type, sorry it isn't clearer.
