As I noted earlier, Bryan Litz has found that while accuracy can be good or even great, when a bullet isn't what many would consider "over-stabilized" then BC is reduced, sometimes enough to make a difference at longer ranges, and certainly enough to make a difference in wind-drift. He's come to the conclusion that a little too much twist is far better than the "minimal ideal" twist.
But whatever. All he done is work for the U.S. Air Force on missile design, thanks to his aerospace engineering degree, been the head ballistician at Berger, started his own company to scientifically study rifle ballistics, and shot on the U.S. Palma team.
Very good statement, John! Probably went over the heads of most.
The key words were "at longer ranges". Bullet yaw due to over spinning decreases B.C. at shorter ranges, as you stated.
Guys shooting the 30BR in benchrest shoot a 1-17 twist that is appropriate for the 117-125g bullets that are VLD's.
Check out Berger's site as a listed for their minimum recommended twist rate for their bullets:
http://www.bergerbullets.com/products/hunting-bullets/My custom 308 had a 1-12 twist and it would shoot tiny groups with all bullets up to the 168g range that was available back then, which agrees with Berger's Minimum twist required. I also worked up loads for the 180g Sierra BTSP and the 180g Hornady BTSP, accuracy again was fantastic.
The poster started this thread wanting to know what was the best twist for 165-168g HUNTING bullets, does not sound like he is a long range shooter, does he?
A 1-14 twist might be appropriate for him if wants to shoot Nosler, Hornady, and Speer cup and core bullets. Also, as you jack up the RPM's on a bullet, cup and core bullets are more likely to shed their jackets quicker. I saw this on predators and smaller varmints when going from 1-14" and 1-12" twists to a 1-9" twists in 22 caliber and 243 caliber bullets. I also found that slowing down the twist rate can also lower pressures, which can allow you to get more velocity. Every barrel is different, and there are no absolutes.
I put a 1-11 twist on a custom 7 STW that has zero freebore and a minimum SAAMI spec chamber, the velocity in this barrel is so fast checked with an Ohler 35P, I will not speak of it.
If a guy does not know what he may want later on down the line, then an appropriate twist rate for the Heavy 200+g bullets VLD target bullets would be a prudent decision.
The standard 30 caliber 1-10 twist has been a tradition for a long, long time. After Remington got busted on putting a 1-12 twist in the 244 Remington, effectively killing the new cartridge, everyone wants to over twist a barrel, just in case...safer to go to a 1-8" twist, just in case he wants to shoot a 240g VLD.
