I know that some rifles in a given caliber shoot lighter bullets more accurately than heavier bullets and vice versa, which can be attributed to its rate of twist. As a general rule of thumb which rate of twist (i.e slow or fast) works best with heavy or light bullets?
Thanks.

In general,the heavier the bullet,the faster the rate of twist required to stabilize it.

It varies by caliber and bullet length. A 30-06 might have one turn in 10" so it can stabilize relatively long bullets (180-220 gr.) A round ball (the shortest possible bullet)will be stabilized by one turn in 60 or 63"

I don't know if this helps or not but Bushmaster rifles almost all of their .223 barrels 1 turn in 9". Their catalog states that the Gov't originally specified 1 in 7" twist but they (Bushmaster) found that 1 in 9" twist gives the best results with the widest range of ammunition and will stabalize most bullets up to 72 grains.

What I heard was that the faster rate of twist is for heavier ammo.