The Firing Line Forums - View Single Post - 1:12 twist won't stabilize 180gr in a 300wm?

Bart B. · January 7, 2013, 10:10 AM

Competitive long range shooters using the .300 Win. Mag. have been using 1:12 twists for 180, 190, and 200 grain match bullets for decades. Same for other cartridges pushing these bullets out at 2900 to 3000 fps. Even 1:12 twists in .308 Win. barrels will shoot 180 and 190 grain bullets with match winning accuracy and they aren't spinning as fast as your .300 spins them. Therefore, your bullets are spun fast enough to stabilize them.

If your 1:12 twist barrel won't shoot bullets of that weight accurate, the problem's not the twist. Something else is not right. Powders close to IMR4350 have worked well with 180 to 200 grain bullets in such magnums. Slower ones may shoot 'em out faster, but typically with less accuracy.

What's the make of your barrel and do you know it's bore and groove diameters? If they're larger than the bullets used, then accuracy will not be all that great. Dimensions need be measured to the nearest .0001". Bullets should typically be at least .0003" larger than groove diameter for best accuracy.

January 7, 2013, 10:10 AM	#2
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Competitive long range shooters using the .300 Win. Mag. have been using 1:12 twists for 180, 190, and 200 grain match bullets for decades. Same for other cartridges pushing these bullets out at 2900 to 3000 fps. Even 1:12 twists in .308 Win. barrels will shoot 180 and 190 grain bullets with match winning accuracy and they aren't spinning as fast as your .300 spins them. Therefore, your bullets are spun fast enough to stabilize them. If your 1:12 twist barrel won't shoot bullets of that weight accurate, the problem's not the twist. Something else is not right. Powders close to IMR4350 have worked well with 180 to 200 grain bullets in such magnums. Slower ones may shoot 'em out faster, but typically with less accuracy. What's the make of your barrel and do you know it's bore and groove diameters? If they're larger than the bullets used, then accuracy will not be all that great. Dimensions need be measured to the nearest .0001". Bullets should typically be at least .0003" larger than groove diameter for best accuracy. Last edited by Bart B.; January 7, 2013 at 11:11 AM.