Way to get started. I would look at a 6 mm or 6.5 caliber, for your other barrel. If you want to be able to shoot the heavier bullets in 6mm, you might consider either a MGM 243 Winchester with an eight twist, or a six Creedmoor, which will probably have a one and 8 twist. 6.5 Creedmoor will probably have a 8 twist as well. This will have a lot less recoil than 308 Winchester, and will be fun to shoot.
Another great little cartridge and 6mm is the 6mm BR. If you don?t reload, you might wanna forget that option