Hi, Vento!
Congratulations on having a fine light-weight rifle!
That .243 Winchester caliber is my favorite deer/varmint combo.
As far as favorite accurate loads go, you probably have to start fresh to find what shoots best in the short, light and whippy barrel. Light, short barrels tend to have their unique vibration nodes and make for picky ammo combination. As I write this, I'm looking at two take-off barrels from M700 lightweight actions that the owners were unhappy with. Not accurate to please them, I guess.
I'd try the classic powder and bullet combinations starting with 70, 85, and 100 grain spitzer and boattail bullets and the medium/slow powders: IMR series, Winchester, and Accurate powders. Be conservative and go with the recommended starting loads. I would estimate a minimum of 20 rounds in each powder/bullet combination to narrow down the best shooters.
Best of Luck, and have fun!