E.Shell
Ultimate Member
This. The longer it is, the faster it has to spin to stay stable....Unless there is some dramatic aerodynamic at work (weird bullet shape), but actually the length of the bullet, not the weight that matters the most....
A common misconception is that bullet weight is the determining factor, but this only applies to bullets of the same construction. Heavier bullets of the same construction are longer than lighter bullets of the same construction. This makes it SEEM like the weight is the key, but length is actually the determining factor.
For example, a Barnes bullet (monolithic copper alloy) in any given caliber will be longer, and thus require a faster twist, than a conventional jacketed lead core bullet that is the same weight.
Another example is that a marginal twist rate will stabilize a round nose bullet (short for its weight) when it will not stabilize the same bullet weight in a long boattail. This is quite well known to handloaders. My 12" twist .22-250 will NOT stabilize a Sierra 69 MK (long for its weight), but WILL stabilize a Speer 70 semi-spitzer (intentionally short for its weight).
Back to the OP, a fast twist barrel will sometimes not shoot light bullets as well, especially if the lighter bullets are not match grade.