One thing you must keep in mind: In most states, the .223rem isn't legal for deer, so you should dually take notice...i.e. make sure it's legal in the state you'll be hunting in...and secondly, MOST people have never used a .223rem for deer because it isn't legal for them...they have no actual experience with the .223 on deer, maybe they've used one on coyotes and varmints, but never deer.

I've never used a .223rem for deer either, but I have used the .22-250, which is quite close in performance to the .223, slightly improved, but close enough for this arguement. Most guns that guys choose in the .223, AR-15s or Heavy bbl bolt guns, are quite accurate, so placing your shot well is easier than say with a standard bbl bolt .30-06, especially moreso than a leveraction .30-30!!! When I hunted a .22-250, I had it in my head that I'd limit my shots to under 150yrds, which is reasonable, it doesn't cut a hunt unrealistically short, but it doesn't ask too much of the round, at that range, I could have shot the deer through the eye off my bipod. Don't make the mistake of using varmint grade bullets on big game, lots of guys hate the 22CF's for losing them deer because they used the wrong bullet.

I hunted deer in TX with a .22-250 Heavy bbl Savage bolt gun, Handloaded ammo with heavy bullets, I can't recall but it seems like they were 75grns even, they were jacketed soft point partitions with bonded core, boat tails...they worked fine, like I said, I cut my range at 150yrds, my actual shots were 68yrds, 44yrds, and 91yrds, the 44yrd and 91yrd deer dropped in a few steps, the 68yrd deer ran about 40-45yrds before collapsing.

The .243win is a better choice by far, I used one for 4-5yrs as a secondary to my .30-06, used it for my second deer of the season after filling my first tag with my .30-06...I really liked it, it's performance was great, recoil and report are low, it was impressively flat shooting and accurate, and the number one thing: it did the job.

If you want it for varmints too, then consider the .243WSSM, it's a considerable upgrade to the .243Win, a goodly bit faster, so it has the flat trajectory that varminters long for. I bought one in the Win 70 Coyote and LOVE it.

If you've got a .223, then use it, if you're buying a new gun, buy a .243win or .243WSSM, they'll better suit deer and they'll still do great on your varmints.