another vote
Here's another vote for the .243. The .243 has become my "light" deer rifle, though I was not a fan for many years, mostly due to ignorance. After watching bamaboy drop several with the caliber, and dropping a few myself, I have no qualms about the .243 for deer, especially under somewhat controlled conditions like over food plots and from shooting houses, where I can pick my shots and a rest is often available.
We shoot the 100 gr Partition, and I have no doubt it will reach the vitals of a deer from about any reasonable angle ( we have not recovered a single Partition, despite hitting one or both shoulders on some shots). I cannot speak to any other bullet or weight, but the combination has been very positive for us on 150lb +/- whitetails.
I hunt other "light" calibers for deer, (7.62x39, and .44 mag) but the .243 has a decided edge on those two numbers with a flatter trajectory due to its higher velocity. (2800-2900 fps in my rifles) Because of that, it is much more versatile than either, and in my mind up to 3 times the effective range (or more, as other posts have indicated). I did not keep track this year, but suspect I may have hunted my .243 carbine more than any other rifles I own last season. No deer with it though, when deer showed up I wanted to shoot, I had other rifles.