In portable breech-loading firearms, the steel frame screwed to the breech end of the barrel, which receives the bolt or block, gives means of securing for firing, facilitates loading, and holds the ejector, cut-off, etc.
The main body of the SKS. This area of the SKS is where the trigger assembly, magazine, barrel, and stock attach to. This is the most stable area to mount a scope.
The basic unit of a firearm which houses the firing and breech mechanism and to which the barrel and stock are assembled. In revolvers, pistols, and break-open guns, it is called the Frame.