Improved gun with automatic loading of cartridges, comprising a cartridge loader in the form of a tubular magazine (4), characterized in that: The magazine bottom (18) is mounted in a way so that it can slide in the axial direction (X-X′) with respect to the tubular magazine (4). The sliding magazine bottom (18) is equipped with a shock absorber (26) able to absorb the shocks exerted on the magazine bottom (18) in the axial direction (X-X′) of the tubular magazine (4). The cartridge follower assembly (19) provided with a shock absorber (29) that can absorb the shocks exerted on the follower assembly (19) in the axial direction (19) of the tubular magazine (4).