I know you didn't mention it, but look at the .220 Swift. It is a small, flat shooting and very, very fast rifle. I was hunting stripey gophers (about the sive of a rat for any one who doesn't know) and he could push that rifle out to 500 yds accurately.
If you are looking at the .243, checkout the 6mm Remington. It is a flatter, faster cartridge and can be used on damn near any game up to elk. For groundhogs, the remington 700 should be able to push 500 yds easy. (just assuming because my model 7 can push 400 easy.)
|