I am more of a 6mm Remington guy than a 243 type. Still, I have owned and used several 243 Rifles.
With the exception of one Remington 700, all had the 1-10" twist. Never had any issues with 100 grain Partitions in any of them.
However, if I had, I would have simply dropped down to the 95 Partition. Not a deer alive (or dead) that would know the difference, lol.
Remington, after the 244 fiasco, changed the twist in their 6mms and 243s to 1 in 9-1/8", so stabilizing most hunting bullets up to 105 grains is no problem.
I have also owned 2 M722 Remingtons with the 1-12" twist. If you loaded them right up there, MOST 100 grain bullets would work, but not all.
The original Remington 100 grain Cor-Lokt, which was quite stubby, shot fine. The later design Remington Cor-Lokt, which was longer, would not shoot.
The Sierra 100 boattail keyholed, the Hornady flat base shot fine. These rifles had 26" barrels, so getting 3200+ fps was not hard....I'm sure that helped a bit.
Any 6mm I have had built in recent years has been with a 1-8" twist, and handle all VLD bullets up to 108 grains.
Regards, Dave