FX Hybrid Slugs & original Smooth Twist barrel?

Nick, Happy New Year pal. I'm always looking to make my guns even more deadly than they already are. I just might have to break down & buy a slug shooter. Don't tell my wife, she'll have my 'nads if I spend that kind of money! 

"Leatherman" any slugs I've tried require a fully rifled barrel. The Smooth Twist barrels are unreal with pellets for accuracy but won't shoot slugs for sh-t. Keeping an eye out for a used slug shooter.