I've tried about 10 factory loadings on deer with my .243, that I've used since 1980...
I've killed about 85 with the 100gr Remington CoreLokt, it does all that needs doing to a deer and my gun groups them very well...That is basically my go to bullet...
I have also killed several with the 100gr Hornady Custom in their SPBT, one of my buddy's guns prefers this over CoreLokts and between us we have killed about 40-50 deer with it...
These 2 loadings are good out to about 300 yards, most deer are killed within 125 or so, so they handle most situations...
A third bullet that is really good is the Federal Premium 85gr Sierra HPBT...If I anticipate shots past 200 yards or so then this is what I use...This bullet will fragment on shots within 50-75 yards, so beware...
Additional bullets that have worked well are the Federal Premium 100gr Sierra SPBT, the Federal Premium 100gr Nosler Partition and the Federal Classic 100gr HotCore...
Hope this helps...