A method is disclosed for preparing metastable nanoenergetic composites (MNC) and for wet loading those MNCs into percussion primer cups. The method involves dispersing nanosize reactants in an inert liquid or, alternatively, making a nanosize reactant surface modification for improvement of reactant's chemical inertness towards water, followed by application of additives supporting a solid reactant particle dispersion in water or water solution prior to mixing. After mixing of the reactants, one maintains the presence of liquid water together within an energetic material in order to enhance safety during pre-loading of the primer mixture into the primer cups and during the final drying.