The Ruger 10/22 is a self contained fire arm. just one screw(2 on some models) holds the entire action and barrel in the stock and it is possible to hollow out an air soft gun (i.e. the FN P90) and safely install the total action and barrel asemmbly. It's also legal as long as you don't modify the action/barrel asembly AND the barrel is 16+ inches AND over all length is over 26 inches. Local laws may be diffrent on total length so it's best to check. You can look online at your states web site to find the rules on firearms.