A system for loading BB-shot into an air weapon includes a loader for storing BB-shot having an aperture, a pressure system promoting forced transfer of the BB shot through the aperture, a cartridge with a cylindrical body having axial channels offset by a predetermined angular pitch for housing rows of BB-shot balls, an elastic occluding member for holding the rows of BB-shot balls in the channels, an intermediate cylindrical element having a passage with an inlet communicating with the aperture and an outlet to be longitudinally aligned to one of the channels, a detaching member interacting with the occluding member for locally disabling it at the outlet and allowing a row of BB-shot balls to be transferred into the channel. The cartridge is rotatable about the longitudinal axis relative to the intermediate element for aligning the outlet of the passage with one channel at a time.