My brother and I have killed 1000s of prairie dogs shooting 22LR, 17 Mach 2, 17HMR, 22 Hornet, .204, .223, 243, and 22-250; all useful depending on circumstances. If you have access to new towns especially with lots of young and dumb dogs, my favorite is the 17 HMR. The 22LR will kill them, but not with the same "whop" factor and you'll have fewer crawl-offs. The Mach 2 works well too, but with a bit shorter range. The 22 Hornet works well out to 150-200 yards and is cheap to reload. It also has very little recoil. We've killed the most dogs with the .223 and .204. Neither round has much recoil. The best centerfire rifle for dogs is a toss up between my Remington 700 VSF .223 and my Kimber 84M .204. If you like to see them fly through the air, the .204 does the job. The big guys are the .243 and the 22-250, but recoil becomes an issue if you shoot a lot. I shoot 58 gr bullets in my Remington 700 VLS .243 and it gives me quite a bit of range, 300-400 yards. My brothers 22-250 gives I'm longer range, but frankly, neither of us is fond of long distance dogs...too many misses. I really like shooting my Anschutz 1517 MPR; the 17 gr V-Max out of that rifle is wicked accurate and effective.