Abstract: A carbine comprising an improved stock assembly kit combined with a barrel and action assembly of preselected generic style or configuration, preferably that of a U.S. M1 carbine. The improved stock assembly includes a buttstock comprised of opposed concave half-sections which embrace and capture the trigger, receiver and operating slide mechanisms of the barrel and action assembly in upside-down orientation. A trigger assembly is mounted to the barrel forwardly of the buttstock section and is coupled to the trigger mechanism of the barrel and action assembly by a trigger slide which extends through the buttstock section. A forehand stock section is comprised of an opposed pair of stock half-sections which embrace that portion of the trigger assembly which engages the barrel and form a cavity for cooling air surrounding the barrel which extends therethrough.