Every Time this subject comes up, does NOT matter if it is the 243, 30-06, 30-30 7mm ECT...
I always Answer.....
What you shoot the BEST thru your Rifle after Testing Different Loads!
As for my personal use in my 243 for Deer, I use either the Federal 70 grain Ballistic Tips or the Hornady 95 grain SST....They both knock the Snot out of Deer and either drop them in their tracks or they only go 25-50 yards! (And they leave blood trails a Blind Man could follow)
The BEST thing for you to do is Get yourself a few different Brands of ammo and work them at the Range and sellect the BEST 2 that shoot the Best and also Read up on Each you choose on how they have performed on Deer!
I use 100 grain RN Hornady, with my reloads. Most all my shooting is close range woods deer. Never had a deer go more than 50 yards after being shot. But like Woody said, no matter if you reload or buy factory rounds you need to try different rounds to find what your gun likes. Just make sure whatever you end up using, the bullet is designed for deer size game.
Back when my son used my 243 for deer I started buying him the Winchester Ballistic Silver Tips. They did a good job on the deer. Trouble is then he wanted them all the time and cost me more money. Any bullet that shoots good at the range will do good on deer. Just put the cross hairs in the right spot and the gun will do the rest. I plan on going back to that caliber when I get older.
i love my 243. this was my first rifle that my father had bought me. when i first started, i used the cheap 100 grain ammo. as i got older i switched to using my 308 and 270, but there is nothing like the 243. last year i took the 243 back out for the first time in a few years, loaded with Wichester Silver Tips. They seem to really hold the tightest groups for me. 160 yard shot, deer dropped right in its tracks, and it really took me back to my younger days. Every different ammo i use shoots a bit different, but i get the best gouping out of the Silver Tips