http://www.atf.gov/firearms/guides/identification-of-nfa-firearms.html#ithaca-auto-burglar
Can the Serbu feed & fire the mini-shells from Aguila?....if so, it could change it from a two-shot to a four-shot & be easier in recoil to boot.....http://www.midwayusa.com/product/162922/aguila-minishell-ammunition-12-gauge-1-3-4-4-and-1-buckshot-11-pellets-box-of-20