Hey BTR, Yes, those 100gr Winchesters should do just fine for you. It sounds as if you do not "load your own" (nothing at all wrong with that), just let your rifle determine which factory load it likes the best and use that one. Sometimes you can change brands of ammo and cut the groups in half, or have the opposite happen.
I've shot a 243Win for many years and the only complaint I have with them is the size of the "Exit Hole" is not quite as large as I like. Doesn't matter if they drop in their tracks, but sometimes they run a little. Due to that, pay close attention to "Nevada Fitch's" post about making sure you follow-up when you get to take a shot.
You are getting good advice from all these folks.
Good hunting and clean 1-shot kills, Hot Core