Our hunting field is densely packed with sage rats. There will be plenty of rats within 100 yards to shoot at.
Most sage rat hunters use rimfire rifles. While you can use centerfire rifles such as .223 Remington or .204 Ruger, rimfire ammunition is preferred because it is less expensive, less loud, and has lower ricochet risks.
The two popular types of rimfire are .22LR and .17HMR. .22LR is effective to 200 yards, .17HMR is effective to 300 yards, although 300 yards is an awful long distance to shoot a rat at. The real advantage of .17HMR is that it drops less at 100 yards than .22LR. .17HMR ammunition tends to be more than twice the cost of .22LR ammunition.
.22LR comes in standard (subsonic or nearly so) and high (supersonic) velocities. Counter-intuitively, when shooting at longer ranges, we recommend using standard velocity. High velocity bullets go transonic before they reach targets past 100 yards, encountering turbulence as they slow below the speed of sound.
The effective range of centerfire ammunition such as .223 Remington will generally exceed your ability to identify small sage rats in the grass. Centerfire ammunition works great, but is more expensive to shoot and is significantly louder.
It is not uncommon to fire 500 rounds in a day of hunting. Time spent loading magazines often becomes the limiting factor. We recommend having plenty of spare magazines and using magazine loaders to speed up the reloading process.