Englisch > Deutsch Sonstige fire weapons

Monolingual German really but since I need help with the translation of the English explanations, here we are:

Relating to the shooting massacre at the Gutenberg Gymnsium at Erfurt.

FAZ : Pumpgun
Spiegel : sogenannte Pumpgun

I would like to explain the function of the weapon in parantheses.

in English:

pump gun - a weapon using pump-action firing
http://www.harcourt.com/dictionary/def/8/2/8/3/8283400.html

pump action - describing a shotgun or other weapon with a sliding mechanism that is moved back and forth manually to clear, reload, and cock the weapon.
http://www.harcourt.com/dictionary/def/8/2/8/3/82830000

Is there a precise German term describing the function or at least one word for 'clearing, reloading and cocking'?

Appreciate any suggestions!
TIA