Adapter devices, apparatus, systems and methods of allowing a firearm to be supported by a foldable fore grip / gun
handle. The fore grip gun
handle can have bipod type legs that can be extendable from the
handle. The fore grip handle can be just a vertical extension. The adapter can allow for the fore grip / gun handle to move from a fold back position along the bottom of the firearm so that the firearm can be easily carried, and the adapter to can allow for the handle to move down to a vertical support position beneath the firearm when the firearm is to be used. The adapter can also support a light in both a folded position and in a downwardly extended position, where light can be aimed forward, rearward to the side and / or pointed down from the firearm. The adapter can allow for a dual functioning component that can be either or both a fore grip and / or a
light source. Other versions of the adapter can include a slidable
thumb switch for locking a swinging plate with picatinny side rails to a main plate, and spring loaded detents for locking the swinging plate in substantially vertical orientations. Additionally, a folding rail
system can be substituted for the existing picatinny rail
system on firearms. The folding rail can have mounting holes for allowing the entire folding rail to be directly attached to the firearm, and have a hinge for allowing portions of the picatinny rails to pivot relative to the rest of the picatinny rails.