You need to consider the pitch of rifling not in terms of inches per turn, but in "calibers" or the numbers of bullet diameters relative to the length of the projectile. The Trap Door Springfield .45-70 had a twist of 20" per turn, and stabilized blunt 500-gr bullets adequately to 1000 yards. the .458 Winchester has a twist of 14" per turn and gives a greater measure of gyroscopic stability to prevent yaw during penetrations of large animals by non-expending projectiles.
A twist as fast as 10" per turn in a .45 caliber would be excessive and unnecessary, but would be a good choice for long pointed boattail bullets such as the 200-gr. Matchking or M72 Match in the .30-'06, or for long, parallel sided 220-gr. roundnosed buletsm, as were used in the Krag rifle.
The Greenhill rule works very well, despite its simplcity. It states that the rifling twist in calibers times the twist in calibers should equal the constant 150. This gives a safe margin of stability to even allow for pointed and boattail bullets. For blunt-nosed, flatbased bullets in target grade barrels with carefully prepared loads you can get good results for target work with a slower twist, but I would not recommend in any circumstances using a twist slower than implied by using the Greenhill formula adjusted by using the constant 200.
If you would like a good lab problem in aerodynamics and engineering mechanics, go to the public library and look up the article by Col. E.H. Harrison, USA (Ret.) entitled Determining Projectile Stability, which appeared in American Rifleman in July, 1962 p. 50.
I wrote a condensed and simplified version which appeared in American Rifleman August 1983 p. 48.
