BATT_RIFLE_* are generally the ones you're looking for, firing non-custom rifles in battle (as in the cut-scenes of Arachnos fighting Longbow)
BATT_RIFLE_LOW_1 and 2 fire while kneeling
BATT_RIFLE_HIGH_1 2 3 3B 4 and 5 are variations on firing while standing (e.g. 5 lowers the rifle and works the action, then raises and fires)
BATT_RIFLE_A1 2 and 3 are more variations.