Faster twists will stabilize a wide variety of bullets, and do reasonably well but... The down-sides to over twisting are three-fold.
In any bullet, going with tighter than neccessary twist will result in more torsional force on the rifle when the round is fired, thus affecting accuracy. Taking a bullet from 0 - 200000 RPM in a millisecond creates phenominal torque.
Secondly, going with a tight twist will wear the throat faster as the bullet slams into rifling at an angle more accute than it needs to be.
Thirdly, light bullets in a tight twist can disintegrate from excesive RPM!
There are the odd exceptions to the rule, but going to a 1:8 will have few if any tanginle benefits to heavy bullets, but will certainly have detriments to lighter ones. In Krieger's case anyting tighter than 1:10 is custom... if it were remotely needed, they would make it.
You may very well be correct on all counts, and your experience is much broader than my observations, but still I offer the following:
1) Should not the shorter bullet be less effected by torque than the longer bullet? Thus, the short bullet should prove more accurate than a long bullet from the fast twist bore. Yet I have observed good to phenomenal results from both light and heavy bullets in a fast twist barrels. Moving from a 1:10 .308 barrel to 1:8 is not such a great departure, but if there is an accuracy detriment to fast twist barrels it should be apparent when I chose the 1:7 to replace the 1:14 factory barrel of my .222. Yet this 1:7 barrel shot almost all bullets exceptionally well. The single exception was the Winchester FMJ bulk bullet (I don't recall the weight, perhaps 62 gr.) which will never be accused of being a match bullet.
2) You might have something here, as a rifle with a chamber cut for a heavy bullet can have the heavy bullet seated closer to the lands than may be possible with a light bullet; thus the light bullet would enter the rifling at a higher velocity. But my head tells me that with a similar jump to the lands, from the initial contact of the bullets bearing surface until such time that the bullet has completely entered the rifled portion of the bore, the forces at play should be similar, regardless of the rate of twist. Otherwise gain twist barrels would have ruled the world.
3) Yes, absolutely correct! A thin jacketed, high velocity, bullet does not respond well to a fast twist barrel. My 1:7 .222 required me to abandon light weight SX and Blitz style bullets.
Precessional velocity is separate from the rotational speed of the bullet, and is defined as the velocity of the center of the base of the bullet around the flight path. In exterior ballistics this occurs at two stages of flight: when the bullet first exits the bore until such time as it can stabilize at some point down range, and again when it impacts the target. From an accuracy point of view, the faster rotational velocity should overcome the precessional velocity that occurs when the bullet exits the muzzle in a shorter period of time, thus improving accuracy.
In a hunting context, there is a theory that given two identical bullets at the same velocity on the same target, the bullet with the faster rotational velocity penetrates deeper. If true, this would result in a no cost advantage to the hunting rifle with the faster twist. The reason for deeper penetration is that the torque applied to each bullet as it contacts the target is more easily overcome by the faster rotation and as a result that bullet precesses less.
Kreiger makes large runs of standard twist .30 caliber barrels. The price he charges for any given barrel is reflected by the number of barrels he has a market for. Palma shooters never shoot other than 154-155 match bullets, thus they choose the twist that is optimum for that bullet weight. Service rifle shooters aren't even aware that bullets other than 168 gr and 173 gr MK's exist, so a 1:10 -1:12 twist is very common. Long Range shooters who want to use heavy bullets don't buy as many barrels, so the fast twist barrel costs more because fewer are made, not because there is less need.
