My 243 ultra does stabilize 100 gr loads, but I to was reluctant to try 100 grain bullets. By definition 1/10 should handle everything up to 100 grains. I am not sure where the twist thing came up but there are guys who say they had key holes in the target.
For me there are three big game bullets to try out Barnes 85 triple shock, Nosler 85 or 95 partitions (have not decided yet probably 95), and the Sierra 85 hpbt. I should also try 100 gr Hornadys.
The Barnes are first on my list because they have a balance of good expansion and great penetration. I shot a small doe this past fall with plain 100 gr loads. The load shreaded her lungs but at the range that I was at there should have been an exit wound. The Barnes I hope will give me that exit wound.