ORIGINAL: Edcyclopedia
There is a lot of .243 lovers and all the power to you, it is indeed a great cartridge and I will not debate otherwise.
As far as the varmint side of calibers the .243 is one of the best choices when you are considering jumping up, to use it for Deer, and probably the minimum IMO.
I chose the .270 for the simple reason of misplaced shots on deer. The .270 will allow for some "Murphy's Law" that happens while hunting.
As an "example" of my claim... While hunting in TX back in 2007, a gentleman gut shot a deer with a .243. Now I'm not claiming that it would have died quicker with a .270, as mentioned it was a bad shot, so let's get that straight. However, after recouping the deer the following day, some 500 yards away, the guided said... In his 28 years of guiding, "the heavy majority of the deer that are wounded are from people that come to camp with a .243". He has always recommended @ least a .270 for this reason, but doesn't enforce it. As he too says "a well placed high percentage shot from a .243 will down a deer just fine".
So there you have it, my opinion why!
If your are a marksman that has never compromised a high percentage shot.
OR
If your deer has never moved / twitched while squeezing the trigger, then a .243 is your poison, a little extra can never hurt though???
So many parents put a small recoil gun in the hands of a novice hunter. And so many times it goes array! If you can handle 243 you can handle the recoil of a 270, there isn't that much difference in recoil, PERIOD(especially with recoil reduction loads)!
Now as described above this is not an issolated incident with a 243, The bullet placement needs to be exact to make a clean and consistant kill. Most excited youths or older folks with buck fever will not make that exact shot kill. NO EXCUSS for bad shots, and I'm not saying that. Practice is the key! However, a better Knock down bullet and penetration will make a potentially bad hunt into a memory? I believe the 270 is the best choice as well. But again it does depend on the shooter abilities and training given over timne. Now this is the key!!!
MHO
Mike