RE: What size rifle do you shoot at deer?
I've used a number, when it comes to deer the list is long. Currently my deerCF is a 7mm rem mag, though wouldn't suggest it in your case since you already have a 300wm and IMO little difference.
I'll start the list of possibles with (no particluar order):
2506 rem (light recoil, flat/fast, accurate and plenty for deer to 400 yards)
270wsm (less recoil then the 300wm but more then the other 2 listed, accurate, fast and flat. Probably the best of thethe 3if your ranges will be 300+)
7mm 08 (enjoyable gun to shoot while benefiting fromthe .284 bullet selection. Not as flat as the other but usually serves the purpose well for most deer hunters where ranges are typically less then 300 yards any way)