First, flush out of your ol' gourd ALL notion that a bullet's weight is the basis for determining which twists (yes, plural) will stabilize it. What matters most is the LENGTH of the bullet.
Once you know HOW LONG the bullet is, if you're comfortable with simple algebra, use the two forms of this equation to figure the range of twists best suited to bullets that are that long. Use
T for the length of the twist (one turn in T inches),
G for the numerical constants 150 and 200,
D for the diameter of the bullet (0.xyz inch), and
L for the length of the bullet (0.bcd inch or 1.pqr inches)
T = G times D times D, divided by L.
The longest twist that can stabilize any given length of bullets is the best twist FOR THAT LENGTH but will stabilize somewhat shorter and longer bullets. If you plan to use a variety of bullets with different lengths, calculate the longest and shortest twist for each length, and choose a twist (if you can) that falls within all those ranges.
If you can't adopt a single twist that falls within all these ranges, go for a shorter, not a longer twist. A twist that's longer than you want just won't stabilize your longest bullets. A twist that's shorter than you want will OVERstabilize your shortest bullets.
IOW, they'll spin too fast for the bullet to tip over with the arc of the trajectory and fly point-on at long range. Instead, it'll fly more and more point-high as the trajectory stops rising, levels over, and arcs increasingly downward. This means that the air resistance of the bullet doesn't fall off as much as the range increases, so at long ranges, its trajectory is shorter (its drop and velocity fall off faster) than a bullet with the same muzzle velocity and a higher ballistic coefficient.
