Twist Rates for a 308
- Thread starter gonziii
- Start date
Garand Guy
New member
1:10
The faster the twist, the longer the bullet you can stabilize at a given velocity.
Most of the hunting rifles use a 1:10 so that 220 grain bullets will be stabilized at as low as 2600 FPS. That's about all the powder you can stuff in a 308 case with a 220 gr bullet on top.
-tINY
For some reason, the 308 has a 1-12 twist. I don't know why but it is suppose to have something to do with the 200 and 220 grain bullets.
Here is a way to check your twist, for sure:
Start a tight patch; being sure the jag is tight on the rod.
Mark the rod with a felt tip to indicate Top Dead Center and a starting point.
Advance the rod until it comes back to Top Dead Center.
Measure the distance traveled from the start mark. That is the rifling twist, one turn in xx inches.
A lot easier than trying to estimate the amount of twist in a foot.
Here is a way to check your twist, for sure:
Start a tight patch; being sure the jag is tight on the rod.
Mark the rod with a felt tip to indicate Top Dead Center and a starting point.
Advance the rod until it comes back to Top Dead Center.
Measure the distance traveled from the start mark. That is the rifling twist, one turn in xx inches.
A lot easier than trying to estimate the amount of twist in a foot.
DAVID NANCARROW
New member
The generally available twist for a 308 Winchester has been 1:12 for decades, however, the 1:10 seems to be gaining in popularity for reasons stated above-it should give you better stability with longer bullets.
Tiny-I don't know how you are getting 2600 fps out of a 220 grain bullet in a 308. Is this a listed load combination anywhere I can look at?
FWIW-I have a couple of Remington VS in 308, both of which use a 1:12, and either one will keep 125-180 grain bullets in a very tight group provided I do my part. From what I can gather in my reading, plus actual field performance, the 180 grain is the heaviest I would choose for any distance shots on game. My favorite is 165 grain bullets for shots out to 300 yards, and has proven to me again and again that it will do the job at top velocities without damaging as much meat as a 150 will.
Tiny-I don't know how you are getting 2600 fps out of a 220 grain bullet in a 308. Is this a listed load combination anywhere I can look at?
FWIW-I have a couple of Remington VS in 308, both of which use a 1:12, and either one will keep 125-180 grain bullets in a very tight group provided I do my part. From what I can gather in my reading, plus actual field performance, the 180 grain is the heaviest I would choose for any distance shots on game. My favorite is 165 grain bullets for shots out to 300 yards, and has proven to me again and again that it will do the job at top velocities without damaging as much meat as a 150 will.
CobrayCommando
Moderator
I think it depends if its a semi-auto or a bolt action. For a semi-auto you're unlikely to be using the heavier bullets.
Nosler and Sierra both make 220 grain bullets in 30 caliber. No reason you can't load them in a 308 case.
It's long, though. Unless you have a long action with lots of room in the front of the magazine or you load one at a time, you'll have to load it pretty far back into a 308 case.
-tINY
2700 fps with 168 and 175 are standard speed. If you are pushing 200 grain @ 2600 fps you are hot loading. My best accuracy load for a 168 grain Sierra HPBT match bullets is around 2790 - 2810 fps and the cartridge OAL is just short enough to feed reliably in my PSS' non detachable magazine. josh
DAVID NANCARROW
New member
Most of my loads for 200 grain bullets run about 2400-2500 fps, and I'm using a 26 inch barrel.
I would guess that you could load a 220 grain in a 308, but you would have velocities around 2300 fps. Depending on the bullet, expansion may not be what you are looking for. TiNY is right-you really need a long throat to keep from crowding the powder, and I can tell you from experience that Rem 700's allow for an overall length of about 2.820 through the magazine.
For pure hunting performance out of a 308, I like the 150 grain softnose for general use, but have noticed at top velocities, it does quite a bit of meat damage, so the 165 grain gets a lot of use.
Both of my 700 VS like the Palma Match 155 grain as well as the 168 and 175 grain SMK.
I would guess that you could load a 220 grain in a 308, but you would have velocities around 2300 fps. Depending on the bullet, expansion may not be what you are looking for. TiNY is right-you really need a long throat to keep from crowding the powder, and I can tell you from experience that Rem 700's allow for an overall length of about 2.820 through the magazine.
For pure hunting performance out of a 308, I like the 150 grain softnose for general use, but have noticed at top velocities, it does quite a bit of meat damage, so the 165 grain gets a lot of use.
Both of my 700 VS like the Palma Match 155 grain as well as the 168 and 175 grain SMK.
.308 Twists
Gonziii,
There is no 1 twist to handle all .30 cal bullets, the low to high grain weight is one of the largest. The twist rate dictates the RPM of the bullet, which stabilizes the bullet.
The easy answer is:
The typical use rounds: 150-175 grn prefer a 1:12 twist (the majority use)
Heavier rounds 180-up prefer 1:10 twist.
Those are your "normal" factory choices. If you are attempting to attain greater accuracy, a lot of other twists come into play that are very bullet weight/ogive specific. IE: the 5-R 1:11.25 is for the 168 & 175 SMK bullet, similarly is the Krieger 1:11, 4 land. Unless you have specific plans and are prepared to spend $3000 + for the rifle only, don't worry about the "unusual/custom twists.
Hope this helps,
LP
Gonziii,
There is no 1 twist to handle all .30 cal bullets, the low to high grain weight is one of the largest. The twist rate dictates the RPM of the bullet, which stabilizes the bullet.
The easy answer is:
The typical use rounds: 150-175 grn prefer a 1:12 twist (the majority use)
Heavier rounds 180-up prefer 1:10 twist.
Those are your "normal" factory choices. If you are attempting to attain greater accuracy, a lot of other twists come into play that are very bullet weight/ogive specific. IE: the 5-R 1:11.25 is for the 168 & 175 SMK bullet, similarly is the Krieger 1:11, 4 land. Unless you have specific plans and are prepared to spend $3000 + for the rifle only, don't worry about the "unusual/custom twists.
Hope this helps,
LP
Twist rates
Gonziii,
A lot depends on what your going to do with the rifle. If your hunting, fine either will do as long as you stay 150 grn or above.
If your punching paper you still will do OK.
If you are competing or any shooting that requires extreme accuracy you'll need to watch the twist rates and the ammo quality.
A 150 grn in a 1:10 twist barrel will do OK, until about 400-500 yrds, then it will get a little goofy. RPM is still high and velocity has dropped. You'll have fair targets at 100, 200, 300,400 they'll spread "pretty big" and at 500 it will be a mess.
If you prefer the light round, I believe Remington also has a 1:14 barrel.
Again, if pure accuracy is what you desire 1) You must use high grade ammo (Match), 2) then worry about the twist for the bullet weight.
Hope this helps,
L Puckett
Gonziii,
A lot depends on what your going to do with the rifle. If your hunting, fine either will do as long as you stay 150 grn or above.
If your punching paper you still will do OK.
If you are competing or any shooting that requires extreme accuracy you'll need to watch the twist rates and the ammo quality.
A 150 grn in a 1:10 twist barrel will do OK, until about 400-500 yrds, then it will get a little goofy. RPM is still high and velocity has dropped. You'll have fair targets at 100, 200, 300,400 they'll spread "pretty big" and at 500 it will be a mess.
If you prefer the light round, I believe Remington also has a 1:14 barrel.
Again, if pure accuracy is what you desire 1) You must use high grade ammo (Match), 2) then worry about the twist for the bullet weight.
Hope this helps,
L Puckett