IMO, the .270 is THE best deer caliber around. I've kilt lots of deer with a .270 and to date all but one have been one shot kills. The one exception was a stupid head shot I was attempting that blew his jaw off, second shot put him down for good. That was the last head shot I ever tried.
A good strong sharp knife and comfortable waterproof boots are a must, I take 2 of each.
I can't say that I've ever needed a sidearm while deer hunting. If you've never done it or seen it done before then the video on field dressing game should be helpful. Practice, practice, practice with whatever rifle you choose. Scout your hunting areas and keep your nose into the wind.
Good luck. It's sometimes better than skill. Let us know how things turn out.
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bullet placement is gun control