The original big .30 was the .30/'03 Springfield and to get the smokeless of the day (1903) to burn they needed a 220 grain round nosed bullet. (Germans were using that .318 bullet at 256 grains I think). Then they improved the powders (and US got the info somehow) and they redesigned... the .30/'06! (Germans went with a .323 bullet and 196 grains I think.) Original twist was for a 220 grain round nose and no one bothered to worry about it since a number of guns were already in use and shot the new 170 grain pointed bullet (boat tailed too???) fine.
Fast twist uses up energy and slower twists have been turned to to get more velocity. The original .250/3000 is case in point. Savage chose 1 in 14 to help get the 3000 feet per second that they were using to "sell" the gun...(With an 87 grain bullet, and there have been no end of complaints that it would only shoot 100 grain round noses accurately...) Later, much later, changed to 1 in 10. .300 Savage is another. .308 is another still. 1 in 12 from the start ... Limited to 200 grain bullets. If 200 grains of bullet is not enough, is .308 enough gun?
Harvey Donaldson wrote of a time when the target boys figured out that the 1 in 11 gave the .308 just a trifle more reliable accuracy and that was a big fad. I think they worked with 1 in 13 too for a time, but it didn't do so well with the 190 grain bullets. Or so I read in his columns. And, if you search, you can find some .308 rifles, many calibers, twisted 1 in 9... Go figure.
So it is your bucks. in 1in 10 is the common standard. Do you lose much going 1 in 11? No. Might you get a trifle more velocity? Yes. Might you lose out on using 250 grain bullets in Africa? Yes. Your bucks, you call... enjoy...
