Yep.....223 gets my vote. Back before I knew anything about varmints and varmint rifles, I looked into .204 and .223. First one I bought was a Ruger #1 .204, followed quickly by a Remington 700 VSF .223. Since then I've acquired another .204, another .223, a 22Hornet, a .243, two 17HMRs, and a 17Mcah2. Just returned from the range testing some new .223 loads. It has been a ton of fun experimenting with both .223s and the many load and bullet options. Great round. But, in the favorite column is a growing appreciation for the 17HMR for prairie dogs. Why? No reloading required!!