Vance, I'm not surprised by that in the lest. Either twist will do to stabilize a 150 grainer, and that bunk about over stabilization is just that, bunk. It'd be like over balancing a tire, or being too balanced when you are standing up, how do you do that? A bullet can be torn apart by centrifugal force, but only a few such are on the market and have to be driven above 4000 fps in 1:7 barrels, we are of course talking about .22 centerfires here. I recently read a very good article on this subject, but my memory has let the source fade away. If I remember, I'll let you know. Basically the author addressed gyroscopic effects, which is what we give a bullet when we spin it, and a bullet that would become unstable from too great an rpm would be unstable, in fact unshootable (from the standpoint of hitting what you are shooting at) at any speed/ rate of twist.
A bullet that is out of balance is out of balance, and no speed of rotation will balance it. In fact, the more unbalanced a bullet is, the more it will deviate (yaw) from the flight path. Higher rates of twists have the effect of multiplying the out of balance condition. That is why we are so concerned with bullets being of equal weight. The more even a group of bullets are in weight, the more equally the mass is distributed in the bullet and the greater the likelyhood of their being "balanced". When we spin a bullet, we are not balancing it, we are stabilizing it around it's center of mass. If the center of mass is off the centerline of the flight path, then the bullet yaws around the flight path and becomes a flyer on the target.
It is the same as fletching on an arrow, the fletching makes the arrow spin which stablizes it along its flight path. Strip the fletching off an arrow and you will see what happens to a bullet with no stabilizing force. It is not a question of balance, it is a question of gyroscopic stablization. Once that is achieved, it doesn't matter how fast you spin it, stabilized is stabilized.
I suspect that benchrest shooters who are using slower twists with lighter for caliber bullets are doing so to gain velocity a sresult of loosing rotation friction in the bore as well as staying in the concept of deforming a bullet as little as possible allows it to be more accurate. How much difference this really makes is measured in thousandth's of an inch, it ain;t gonna matter where the rubber meets the road or more to the point where the bullet hits the game. However, stick a 220 grainer in that 1:12 and you would likely get funny oblong holes in your target, if you could hit it at all, as required twist is a function of bullet length not weight.
