Actually, many of the older .244s with the slow twists shoot 100-grain bullets just fine. If it were my .244, I'd try shorter 100-grain bullets like the Remington CoreLokt and the Speer HotCore before I gave up on heavy bullets. These bullets are shorter than most other 100s like the Noslers PTs and BTs, Sierra BTS and Hornady SPs. Shorter bullets are easier to stabilize in slow twist barrels.
If it won't do well with short 100-grain bullets, I had good luck with the 85-grain Nosler Partition on smaller deer with my 6mm Remington. IMR4350 worked best for me.