Marlin 1894 and Ruger Old model both in 357
I would take my Marlin 1894 with a Marbles taang sight and a Ruger Old model blackhawk both in 357. These are simple weapons and anything that broke could be made or fixed by just about any good blacksmith. Having the same ammo would mean reloading would be easier, a Lee 310 tong tool would resize cases, size bullets, deprime and reprime, seat bullets. With a four cavity mold with 4 different cavities, a 180 gr FN, 158 gr SWC, 140 gr RN and 147 WC, would cover just about any situation. Powder could be suplanted with the old stand by of fffg, the only problem would be maintaining a supply of primers. I figure about 200 rounds, a pound of 2400 and a pound of 231, 10,000 primers and some pre cast bullets with gaschecks. You would also need a small pot and ladle.
I would like to see your fast and smooth AR run after about 10 rounds of blackpowder.........