J E,
Don't get me wrong here, I'm not looking for an argument here either. That's really not my style. However, from your comments, I don't think I made myself clear. I never said the manufacturers lied about their twists. I promise you, they are as honest as they can possibly be when stating the twist rate of a given barrel. But there are problems in making barrels that result in a certain plus or minus when rifling it. In other words, that 1x9" may be a 1x8.5" or a 1x9.5", something like that. As I said, this is particularly true with buttoned barrels. Twist rate in these barrels is controlled by the pitch in that carbide button as it is either pushed or pulled through the bore, and is subject to speeding up or slowing down as it encounters hard or soft spots in the barrel. So, while the button may indeed be cut properly to produce a true 1x9", there are other factors that may cause this to vary somewhat. This is why I always advise to go slightly faster than whatever calculation leaves you with a stability factor of 1.1 or 1.2. Benchrest shooters may not agree, but for the rest of us, a stability factor in the range of 1.5 to 2.0 is far better for a hunting rifle. Cut rifled barrels are mechanically controlled during the cutting process, more rigidly locked into their twist rates, as it were. They tend to be a bit closer to their stated twists, which can be a good thing if you're flirting around that borderline stability area. Now, which is better? That depends on the care the barrelmakerputs in and the quality of his work. There are truly superb barrels out there made by just about every imaginable process. Just as surely, there are so-so and really lousy barrels by every process as well. On my own competitive guns, I have cut barrels, buttoned barrels and eve a few hammer-forged barrels (a couple of truly superb old Winchester Ultra Match barrels made 30+ years ago), and they all shoot very, very well. Over the past twenty years I've burned up literally hundreds of Hart (buttoned) barrels, and have found them to be outstanding. Wouldn't have kept using them if they weren't. Ditto for Satern (cut), Krieger (cut and buttoned) and a host of others. As I said, it's a question of the care and quality of the maker, not the process.
That said, the actual (true) twist rate of the barrel is only one factor that comes into consideration here. Yes, the physics issues here are hard and fast, but you do see things that don't quite match the results of all that head scratching. The answer there isn't that the rules are wrong, but that there's something (or more likely, several) that wasn't accounted for in the equation. The issues that go into these problems can be staggering, and most of the formulas that allow us to come up with a quick and dirty twist prediction (Greenhill comes to mind) are simplified by overlooking or omitting several of these. It works, but there's wiggle room built into them. That, incidentally, is why they tend to be so conservate (again, like the Greenhill).
J E, no argument intended here, I hope it isn't taken that way. Just trying to shed a little more light on a very complex topic. If you want to get a better view on this, I'd recommend Moder Exterior Ballistics, by the late Bob McCoy. Bob was an aeroballistician with the Army's ballistics lab at Aberdeen Proving Ground, and had the opportunity to test every theory, every change, every new idea that came along for over twenty years on a range that was fully instrumented to learn about every aspect of a bullets flight imaginable. If there's a question, chances are Bob answered it at some point. He was a neat guy, and a very dedicated shooter himself.
If I have left anything out, bring it up and we'll see if we can't figure it out.
Kevin Thomas
Berger Bullets
