C.R.S. § 18-12-401

As used in this part 4, unless the context otherwise requires: (1) Intentionally left blank —Ed. (a) “Firearms” means a pistol, revolver, or other weapon of any description, loaded or unloaded, from which any shot, bullet, or other missile can be discharged, the length of the barrel of which, not including any revolving, detachable, or magazine breech, does not exceed twelve inches. (b) “Firearms” does not include firearms, as defined in subsection (1)(a) of this section, for which ammunition is not sold or which there is reasonable ground for believing are not capable of being effectually used.