Ok, you have two rifles, identical except one is a 1-8" twist barrel, the other is 1-12" twist. No fast/slow barrels, we are talking theory. With identical loads, will one have a faster starting velocity? Produce more pressure? Sow down fsater? Show greater resistence to being blown by crosswind? At equal impact speed will one have more energy? Finally, is rotational speed independent of forward velocity, or will both slow down proportionally? I know that twist has an effect on stabilizing bullets, just wonder if it has other effects as well?

I've heard that the faster twist will cause slightly higher pressure with the same load, have also heard claims that the slower twist will allow slightly velocities.

I've never calculated what component of potential energy that the rotational component consists of.

Rotational velocity does not slow down as quickly as straight line velocity, in fact there is very little loss of rotational speed in the short time a bullet is traveling to the target.

One thing a faster twist will aid is the bullets expansion when it hits flesh. Bullets that spin faster open up faster.

And!! Bullets that spin faster ruin more meat. Not a big deal in a state that lets you have a couple of deer whatever but in Oregon? One small Blacktail? Want ALL the meat I can get. As a friend said one time while my wife was boning out a deer-- Wow! Leave something for the dogs! Not likely. Just my .02
Aloha, Mark

I've read it makes little difference in pressure, unless the twist is extremely fast.

The energy stored in the moving bullet is about 99.7% in the forward direction; the rotational energy is small. If the rotational energy is small, the forces producing it likely are as well. However, if you have a 1 in 0.1" twist, you're looking at something of a bore restriction, so this energy analysis has its limits.

Let's look at it this way. For 30 caliber, a 1:8" twist is a ramp of about 7 deg and a 1:12" twist is about a 5 deg ramp. Look at this angle as where you're pushing down on a weight sliding along a horizontal surface. Yes, the friction increases by pushing at a 7 deg angle instead of 5 deg, but compared to the bullet engraving and inertial forces, this won't be much.