A retractable support assembly for a firearm. The assembly includes a swiveling support structure configured for attachment to or adjacent to the forward end of a firearm extension component on the firearm. The support structure, when attached, is substantially centered on the longitudinal axis of the firearm barrel and permits movement of the longitudinal axis of the firearm barrel relative to a position fixed by deployment of the assembly for variable aiming of the firearm. The assembly includes a plurality of legs pivotably connected to the support structure for movement between an extended position wherein the assembly supports the outer end of the longitudinal axis of the firearm and a retracted position. The assembly also has a leg-locking mechanism connected to the support structure for locking the legs in the extended position.