Examples of a ‘slam-barrel’ pistol, a design in which the barrel also acts as a striker against a fixed firing pin located at the rear. The barrel is pulled forward to cock and load a cartridge.
A fairly compact improvised semi-automatic pistol seized in Brazil. Its entire trigger frame is from a paintball marker.
Pictured is an interesting improvised 9mm firearm being sold within criminal circles in Brazil. The entire trigger group / lower is from a standard paintball marker, allowing for a more useful semi-automatic (open-bolt) operation. A clever feature is the use of standard 9mm holed hexagonal brass bar stock as a crude smooth-bore barrel.