The best approach is to get a Hammond Game Getter.
http://www3.telus.net/gamegetter/operate1.html
This is a centerfire case for your rifle with an off-center primer pocket. On examination, you see the "Primer pocket" is actually a chamber for a .22 rimfire -- it's off-center so the centerfire firing pin will hit the .22 rim. You load it with a nail-driving .22 blank and a sized buckshot (you get a simple sizing die with the kit.)
Mine, for a .30-06, will shoot about 1 1/4" groups at 25 yards, printing right on top of the end of the thick bottom crosswire. I've harvested quite a few squirrels while sitting in a deer stand.