One this day a few miles west of Idaho's boarder in 2004 the low man in the group shot 700 rounds, high man shot 1200 with an Anschutz .22mag Sporter (4rd mags) at Oregon's Belding digger squirrels that invade alfalfa fields. Basically Coors Light can size +/- 1-1.5". All were shooting .22mag.
I had days with my AR .223 24" barrel purchased in '92 that I've shot over 600 rounds and 3-400 rounds of rimfire. Our targets range from 25-350yds typically, though 642yds is my 'record' with the AR.
I now take .22lr pistol, .17HM2, .17HMR, .17WSM, .223 AR, .223 Tikka Varmint. The field/location/range may limit the you to rimfire or may dictate centerfire is required.
This was 2003 in central Oregon, my brothers shooting. The center of the pivot is 318yds. and the entire field was covered with squirrels.
Shoot what makes it fun and safe for you. Bigger the round, bigger the pop and acrobatics. The .17HMR is a great happy medium under 175yds.