The Firing Line Forums - View Single Post - TWIST: Difference in handgun vs. rifle for same caliber

James K · July 13, 2013, 09:21 PM

The main factor in determining rifling twist is not the barrel length but the bullet length and the ratio of diameter to length. A longer bullet (like most rifle bullets) will require more twist for stability. Most handgun bullets are pretty short (imagine a .30 caliber 220 grain bullet in a .32 ACP case!!) so require a slower twist.

For rifles like the .30-'06 which is loaded with a wide variety of bullets, manufacturers choose a compromise twist rate (usually 1:10) which will be OK for the medium bullet range (150-180 grain) but perhaps not so good at the extremes (110-220 grain).

Jim

July 13, 2013, 09:21 PM	#3
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	The main factor in determining rifling twist is not the barrel length but the bullet length and the ratio of diameter to length. A longer bullet (like most rifle bullets) will require more twist for stability. Most handgun bullets are pretty short (imagine a .30 caliber 220 grain bullet in a .32 ACP case!!) so require a slower twist. For rifles like the .30-'06 which is loaded with a wide variety of bullets, manufacturers choose a compromise twist rate (usually 1:10) which will be OK for the medium bullet range (150-180 grain) but perhaps not so good at the extremes (110-220 grain). Jim