Pump action

Also because the action is cycled in a linear fashion, it creates less torque that can tilt and throw the gun off aim when repeat-firing rapidly.

[1] Alexander Bain of Britain patented a pump action harmonica gun in 1854 that was actuated via a sliding piece underneath the barrel.

However, some pump-action shotguns and rifles, including the Russian Zlatoust RB-12, Italian Valtro PM5, American Remington 7600 series, and the Mossberg 590M, use detachable box magazines.

A pump-action firearm is typically fed from a tubular magazine underneath the barrel, which also serves as a guide to the movable forend.

Only a few pump-actions use the "reverse" or forward-and-back motion of the forend to cycle the action, a few examples are the Russian RMB-93 and South African NeoStead 2000.

As the forend reaches the rear and begins to move forward, the elevator lifts up the shell, lining it up with the barrel.

It's not uncommon to see extra ammunition stored in externally mounted "shell holder" racks (usually as "sidesaddle" on one side of the receiver, or on the buttstock) for quick on-field reloading.

The shells are chambered and extracted by pulling/pushing the sliding fore-end enveloping the tubular magazine toward the user.

In the late 19th and early 20th century it was referred to as a trombone action, because it functioned similarly to the musical instrument of the same name.

[16] A "reverse pump-action" design can sometimes be found, where the extraction is done by pushing the fore-end forwards, and re-chambered by pulling backwards.

[17][18] The Semprio is a reverse pump-action system that ejects cartridges when the fore-end is pushed forward and loads the chamber when pulled backward.

The Semprio's 7-lug bolt head design displays a locking surface of 65 mm2 (0.101 in2) compared to the 56 mm2 (0.087 in2) of the Mauser M98 bolt-action rifle.

The 43mm GM-94 is a pump-action grenade launcher developed by the KBP design bureau for use by Russian special forces.