It is a blast (no pun intended) isn't it? I reload black powder too for my old guns; '73 Winchester 44-40 rifle, .45 & .38 cal. revolvers and 16 ga. outside hammer shotgun. Is your 43 Spanish a Remington rolling block? Patched bullets increase accuracy like mad and improve bore performance.
Yes, when I wanted to get a rolling block, I noticed that the Number 5s in 7mm were going for $400-500, but the Number 1s were only $200-300. I figured the availability of the ammo was a big reason for the difference. I paper-patch the Martini because that is the historical round for that gun. It is neat ending up with rounds that look like pictures of the old rounds with the little white band just above the brass. The shoot as smooth as silk, too. My 43 spanish keyholes wickedly, but I haven't tried paper-patching that yet. Were the original rounds for that paper-patched?