All I can offer at the moment is SAAMI’s glossary definition:

Action, Hinged Frame – A design wherein the barrel(s), one or more being either smooth or rifled, is pivoted on the frame. When the action is open, the barrel may pivot up or down or sideways for loading or unloading. When the action is closed, the breech of the barrels swings against the standing breech. Opening is normally accomplished by movement of a top or side lever.

guns that use a hinged frame action:

• . . .

 

Footnotes / Sources:

“Glossary ⇒.” Sporting Arms and Ammunition Manufacturers’ Institute. Ed. SAAMI’s Technical Committee. Web. 15-18 Jan. 2011.

 

Question:

• Do you know of a gun that uses a hinged frame action?