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Hatcher's Notebook is a good place to look for a discussion on theoretical twist rate.

Bulldog: Longer bullets need to be spun faster to stabilize. Longer bullets are generally heavier, but it aint necessarily so! Military Mk7 .303 bullets were made with an aluminium nose-cone to increase BC, as were the Holland Magnum Paradox projectiles. Hollow-points are another case in point (!), and the 12-bore WR Explora projectile had a fully-enclosed hollow copper nose.

Also, remember that a bullet might be quite stable from the muzzle to say 100 yds, but as its velocity falls away its rpm will be reduced and it could become unstable and begin to tip or tumble before reaching say 150 yds.