Here's an easy way to never run out of rimfire targets (granted, you do need an accurate rifle, a scope with plenty of magnification, and a good rest). Take a 2x4" and set it up at 50 yards distant. Fire five shots at anything you want, but be sure and recover the spent shell casings. Line the five spent shell casings up on the edge of the 2x4" and have at it. Every shot you take generates a new target. Done right, it looks like this: