Small size AgX (X = Br, Cl) nanoparticles have been synthesized by a novel solid-solid reaction performed by mixing two dry dispersions of AgNO3 and KX nanoparticles in AOT/n-heptane solutions. UV-vis investigation ascertained that formation of nanosized particles taking place after the mixing process is fast and complete. Microcalorimetric measurements of the thermal effect coupled with the mixing process suggest the occurrence of confinement effects and adsorption of the surfactant molecules at the nanoparticle surface, hinting at formation of charged nonstoichiometric surfactant-coated nanoparticles. The analysis of SAXS spectra shows that salt-containing AOT reversed micelles are slightly bigger and more polydisperse than bare AOT ones. After the mixing process, from all liquid samples, interesting AgX/AOT composites at high AgX nanoparticle concentration can be prepared by simple evaporation of the organic solvent. Size, polydispersity, and crystal structure of AgX nanoparticles embedded in AOT matrix were determined by WAXS and TEM.