Hagar, regarding this 22 caliber 1:12 twist vesus a 1:9 twist. . .the 1:9 one presents a greater rifling angle to the bullet than the 1:12. A .22 inch diameter bolt with 20 threads per inch has a "twist" of 1 in 1/20th inch. Therefore, with all other things being equal, the 1:9 twist barrel will shoot the same round with a tiny bit more peak pressure. Not enough to be concerned about and very hard to measure.
Note that a 22 caliber 1:8 twist presents the same rifling angle to bullets as a 1:11 twist in a 30 caliber barrel.
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Last edited by Bart B.; February 15, 2013 at 08:23 AM.