A mechanism for feeding uniformly-sized spherical projectiles such as paintballs into a gun adapted to shoot said projectiles is positioned in a lower region of a paintball-holding magazine, and includes a spinning body in the form of a spool from the peripheral side of which project radial arms shaped and dimensioned to urge projectiles toward a duct leading to the ammunition intake port of the gun. The spool is driven by a switchable electrical motor. In order to avoid gaps into the row of paintballs that are urged toward the ammunition intake port when the motor is not running which could result in dry firing, a resiliently variable linkage between the propelling arms is provided by a spiral spring or a pair of stretchable coil springs.