Congratulations on your interest in shooting the Remington rolling block rifle!
I've collected and shot the various obsolete black powder rolling block calibers for several years and will share some info with you.
The .43 Spanish is probably the most often reloaded and fired of the old military calibers other than the .45-70 and .50-70. It is also the most cantankerous to load, with expensive brass and non-standard sized bullets. Components are available from several black powder cartridge suppliers online. Case life is usually poor, and case head separations happen after only a couple firings.
eap
The .43 Egyptian is not commonly reloaded but can easily be done using fireformed/mouth annealed .348 Winchester brass, shotgun powder, and tissue paper plugs. The .348 Win brass is strong and cheap. Bullets are as non standard as the .43 Spanish, but Lyman molds and bullets are available. The downside is that surplus Egyptian rolling blocks are usually found in terrifically bad condition from decades of egyptian and police use/abuse/non-maintenance. You might get lucky and get one with a good bore.
The upside of loading and firing these old calibers is that reloading can be very simple and cheap. A decapping punch, a block of hardwood, and mallet are all that is needed. Prime cases by tapping or pressing case against a flat piece of hardwood. Fill cases full to base of seated bullet using FFg black powder (ONLY!!!!) and seat with lubricated lead bullet. Case mouth resizing is not needed, but if bullet seats too loose, squeeze mouth to fit, or have a machinist make you a simple neck sizing die for use with a mallet.
Have fun, and let us know how you make out!
John
.
