I've got 2 groundhog rigs a 223rem and a 6mmrem that i use for deer and ghogs. If they actually made guns in the caliber still very few doand ammo wasnt really hard to find and pricey i'd say a 6mmrem would be the way to go. I've busted hogs alot farther than i shouldve been able to with that 6mm. 223 works great though also. I've busted hogs with it out to 350yards on more than one occassion. I have a savage model 110 custom stock and trigger job and its a real shooter. 50gr Hornady Vmax's and the groundhogs dont go anywhere. As far as the handi rifles go i had one in a 243win and i wasnt overly impressed by it I killed deer and groundhogs with it but I never was really confident in the gun so i traded it off. Alot of people really love the handi rifles though!