.308 Rate of Twist?

170 grain FP · June 9, 2010, 10:24 AM

Hello all,

I'm new to the forum but have some experience with firearms and handloading.

Anyway, I did up a batch of reloads for my grandfather's pre-'64 Winchester M70 in .308 (1952, I think). It is pretty darn accurate with 150 gr factory ammunition but with both my 180 gr handloads and 180 gr factory ammo the accuracy suffers noticeably. I was running 180gr Sierra gameking handloads with x amount of H4350 and a CCI large rifle primer. I don't have the data on hand but that is what I remember.

What got me thinking beyond a not-so-good handload combination was the fact that the rifle was less than impressive with the 180 gr factory ammo. Does the rifle not have a rate of twist able to stabilize the bigger 180 gr bullet compared to the 150? I was thinking that maybe back in the '50s people weren't planning on shooting the bigger stuff out of the .308.

**Unclenick** · June 9, 2010, 11:11 AM

Welcome to the forum.

Your barrel is likely to have either a 10" or 12" twist. The former, at sea level and in non-winter temperatures, will stabilize 240 grain round nose bullets and 210 grain very long, pointy VLD bullets. The 12" is fine with most 180 grain long pointy VLD's and with 200 grain round nose shapes.

So, it is unlikely to be twist and more likely that the higher recoil is disturbing the muzzle position more and that your load has a barrel time that causes the bullet to exit when the disturbance is excessive. You can adjust the loads to change the barrel time to find a dead spot in the disturbance, and that is what is meant by finding a so-called sweet spot load. You may find more than one. Dan Newberry's OCW site has a good systematic method for accomplishing this.

Jim Watson · June 9, 2010, 11:32 AM

Agree with Unclenick.
That early a .308 almost surely has a 12" twist... which is ample for a 180 grain bullet.
Grandpa's .308 might just not "like" the 180. Try a 165 if you want something heavier than 150.

170 grain FP · June 9, 2010, 01:17 PM

Thanks guys,

This does make sense. It was during the dead of winter that I tried out these handloads and I guess I had been lucky thus far with powder/bullet combos with .270, .30-30, .30-06. You live, you learn. Time for more experimenting!

5R milspec · June 9, 2010, 08:16 PM

hey if you do not mind the recoil why not try a 208gn A-max.my 5R with a 11 1/4 twist likes them.R17 or varget are the two powders of choice.with a 24 inch barrel with R17 47.5gn is my load.but with varget I would start a test at 42gn and work up.and yes the bullet will shoot out of your 1:12 twist.the guy who started this 208 thing shoots his out of a 20 inch 1:12 barrel.I am getting 2800 fps in my rifel with R17.haven't tried varget yet.but in the 20 inch tube the guy is getting 2500 fps or right at it with 43 . something grains of varget.and I have to say they shoot great with alot of energy.

sorry about this just read your thread again to make sure I was giveing out good info.1952 rifel might not want to load up the 208's for it.but the 165-8 should work out for ya.but still think the 1:12 1952 barrel will shoot the 180 and up bullets.but hey atleast you have some new info now.

June 9, 2010, 10:24 AM	#1
170 grain FP Junior Member Join Date: June 9, 2010 Posts: 2	.308 Rate of Twist? Hello all, I'm new to the forum but have some experience with firearms and handloading. Anyway, I did up a batch of reloads for my grandfather's pre-'64 Winchester M70 in .308 (1952, I think). It is pretty darn accurate with 150 gr factory ammunition but with both my 180 gr handloads and 180 gr factory ammo the accuracy suffers noticeably. I was running 180gr Sierra gameking handloads with x amount of H4350 and a CCI large rifle primer. I don't have the data on hand but that is what I remember. What got me thinking beyond a not-so-good handload combination was the fact that the rifle was less than impressive with the 180 gr factory ammo. Does the rifle not have a rate of twist able to stabilize the bigger 180 gr bullet compared to the 150? I was thinking that maybe back in the '50s people weren't planning on shooting the bigger stuff out of the .308.

June 9, 2010, 11:11 AM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	Welcome to the forum. Your barrel is likely to have either a 10" or 12" twist. The former, at sea level and in non-winter temperatures, will stabilize 240 grain round nose bullets and 210 grain very long, pointy VLD bullets. The 12" is fine with most 180 grain long pointy VLD's and with 200 grain round nose shapes. So, it is unlikely to be twist and more likely that the higher recoil is disturbing the muzzle position more and that your load has a barrel time that causes the bullet to exit when the disturbance is excessive. You can adjust the loads to change the barrel time to find a dead spot in the disturbance, and that is what is meant by finding a so-called sweet spot load. You may find more than one. Dan Newberry's OCW site has a good systematic method for accomplishing this. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; June 9, 2010 at 12:16 PM.

June 9, 2010, 11:32 AM	#3
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,539	Agree with Unclenick. That early a .308 almost surely has a 12" twist... which is ample for a 180 grain bullet. Grandpa's .308 might just not "like" the 180. Try a 165 if you want something heavier than 150.

June 9, 2010, 01:17 PM	#4
170 grain FP Junior Member Join Date: June 9, 2010 Posts: 2	Thanks guys, This does make sense. It was during the dead of winter that I tried out these handloads and I guess I had been lucky thus far with powder/bullet combos with .270, .30-30, .30-06. You live, you learn. Time for more experimenting!

June 9, 2010, 08:16 PM	#5
5R milspec Senior Member Join Date: December 11, 2009 Location: South Carolina Posts: 360	hey if you do not mind the recoil why not try a 208gn A-max.my 5R with a 11 1/4 twist likes them.R17 or varget are the two powders of choice.with a 24 inch barrel with R17 47.5gn is my load.but with varget I would start a test at 42gn and work up.and yes the bullet will shoot out of your 1:12 twist.the guy who started this 208 thing shoots his out of a 20 inch 1:12 barrel.I am getting 2800 fps in my rifel with R17.haven't tried varget yet.but in the 20 inch tube the guy is getting 2500 fps or right at it with 43 . something grains of varget.and I have to say they shoot great with alot of energy. sorry about this just read your thread again to make sure I was giveing out good info.1952 rifel might not want to load up the 208's for it.but the 165-8 should work out for ya.but still think the 1:12 1952 barrel will shoot the 180 and up bullets.but hey atleast you have some new info now.