There is no such thing as an ultimate varmint rifle. I use a battery of rifles in various calibers. Three Savage Precision Target Action based rifles with a series of easily swapped barrels and bolt heads, so I can tailor them to the need. Remingtons, some with Savage style swap barrels for the same purpose, some not. A Cooper, a Sako Benchrest, and a rimfire or two.
Cartridges include: .17HMR, .204 Ruger, .223 Remington, .22-250 Remington, .22-250 Remington Ackley Improved, .220 Swift, 6mm PPC, .243 WSSM, .257 Roberts Ackley Improved, 6.5x284. Some have more than one barrel with different twists for different bullets. All depends on what is begin hunted and where.
My favorites and the most flexible are the .204 Ruger, .223 Remington and the .243 WSSM - the later for long range and sheer spectacle of atomizing ground squirrels. The .204 Ruger seems to be the hands down most fun, and even when I think I missed - I find a splat.
