Morphologies of AgI _1-xBr _x (0 ≥ x ≥ 1) nanocrystalline structures formed in carbon single-wall nanotubes (SWNT), of diameter d = 11.5-17.6 Å, have been investigated by molecular dynamics simulation. For AgI _1-xBr _x in a (10, 10) carbon SWNT (d = 13.54 Å), ionic motion characteristics at different temperatures have been studied. Calculations confirm the experimentally based suggestion that structural differences between AgI and AgBr in carbon SWNTs are less pronounced than in the bulk crystals. According to the simulation results, in tubes taken out from the melt, AgBr and AgI _1-xBr _x tend to form hexagonal nanotubes after annealing, similar to those formed by AgI. A superionic state, with significant silver ion mobility against a stable anion sublattice, can be observed in the simulated AgI _1-xBr _x@SWNT; the superionic conduction temperature range shifts downward with increasing bromine content. At temperatures below and just above the nanocrystal melting point, ion migration is faster in more bromine-rich AgI _1-xBr _x@SWNT systems, while at T ≥ 1000 K, the composition dependence of ion diffusion coefficients is much less pronounced. Just as in AgI@SWNT systems, the ion transport characteristics change significantly with a transition from single-wall AgI _1-xBr _x nanotubes in carbon SWNTs to structures with extra ions in the tube center.