Welcome to HNI.

As far as caliber, I think many would consider the 243 Winchester appropriate for deer but somewhat underpowered for anything with a bigger, sturdier build. There are two Ruger rifles you might find appropriate that come to mind. The Ruger American is a relatively new economy rifle that can be chambered in the 243 cartridge. If you're looking for an older rifle, there's the Ruger M77, also made in 243.