Just a guess, but from your handle I would guess it will be for groundhogs. If so, my all time favorite round for the Contender carbine is the .17 AH. Mine likes the 19 gr. Calhoon bullets and shoots point blank to about 285 yrds. or 290 yrds. It only uses 10.4 grs. of powder and with the Calhoon bullet It seem to kill them so fast that I very seldom get the tail screw.