Barrel twist equals stabilization: Truth, lies, myths, total BS, basic guidelines or some is and some aint?

[Beelzebub]

I've read many threads that say to stabilize a 6MM Sierra BTHP Match bullet you have to have an 8 twist barrel. I have a pair of old shot out Remington 700 243's in VLS. Both are 9.125" to 1 twist. Both will shoot the aforementioned bullet into a 3 shot one hole group at 100 yards. I have an RPR 243 with a 7.7:1 twist. It will shoot 10 shot groups under a half inch at 100 yards with the Berger 115 grain VLD Hunting bullet. SO I was wanting to shoot some of the higher BC Sierra 110 grain match bullets. My two old Remington barrels key-holed every one of them. So I looked and waited and looded and waited until I found what was advertised on GunBroker as a Remington Model 700 with a Lilja 8:1 twist barrel that hadn't been shot more than break in. seller was an A+ 4000+.

So this morning I boogied over to my new range to shoot this new/used rifle. Bore sighted it early this morning when I could see crosshairs and the lazer against the side of my white boat at 100 yards. Boat is in the back yard. I didn't haul it to the range ;-) Well, how disappointed was I when the first bullet in the target was a keyhole! And so were the next 9. The 110 grain bullets were seated a little longer to get a tad more powder in them safely and were actually 25 feet per second faster than the 107's With tail between my legs and my heart broken, I pee'd on the fire and called in the dogs and came home. So I guess I'll try the corn cob on stick trick and see if I can get a rough guess on the twist of this new rifle. BTW, the only markings anywhere on the barrel are 243.

 

[jebel]

Rather than relying on hearsay for what twist rate will stabilize a particular bullet, before you buy plug the figures into an online calculator.

JBM's calculator is here: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

If you need the length of the bullet for the calculation, you can get that from JBM also, here: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Plugging in the 110g Sierra Matchking (.243) with a bullet length of 1.335 inches and a velocity of 2,863 fps in a 1:8 twist barrel results in a stability factor of 1.248 at sea level. That's too low, in my book. I want to see at least 1.5 or above. FYI, the the 107g Sierra Matchking should stabilize in a 1:8 twist (stability factor above 1.5).

Last, you should manually check that new barrel's twist rate. It might not actually be 1:8.

 

[Wedgy]

I think that's what he meant by "So I guess I'll try the corn cob on stick trick and see I can get rough guess on the twist".
Many factory barrels are incorrectly labeled on the twist rate.

 

[Beelzebub]

Rather than relying on hearsay for what twist rate will stabilize a particular bullet, before you buy plug the figures into an online calculator.

JBM's calculator is here: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

If you need the length of the bullet for the calculation, you can get that from JBM also, here: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Plugging in the 110g Sierra Matchking (.243) with a bullet length of 1.335 inches and a velocity of 2,863 fps in a 1:8 twist barrel results in a stability factor of 1.248 at sea level. That's too low, in my book. I want to see at least 1.5 or above. FYI, the the 107g Sierra Matchking should stabilize in a 1:8 twist (stability factor above 1.5).

Last, you should manually check that new barrel's twist rate. It might not actually be 1:8.

My point was, how does only 3 grains make such a horrendous difference? I haven't done an exact comparison on the 107 versus the 110 but how much different could they be? So 3 grains difference from bullet to bullet and to a considerably faster twist (9.125 to 8) if it truly is that. Then an 5 grain increase in bullet weight from 110 to 115 with only a .33 twist increase and we're back way below sub MOA again.

I'm so afraid now that I'm going to find out the supposedly Lilja barrel is a 9.125 or worse 10 twist! And to make it worse, the sub .25" group 107's won't let the bolt close in Remington 700 #3. (four letter words here)

 

[ShtrRdy]

My point was, how does only 3 grains make such a horrendous difference? I haven't done an exact comparison on the 107 versus the 110 but how much different could they be? So 3 grains difference from bullet to bullet and to a considerably faster twist (9.125 to 8) if it truly is that. Then an 5 grain increase in bullet weight from 110 to 115 with only a .33 twist increase and we're back way below sub MOA again.

I'm so afraid now that I'm going to find out the supposedly Lilja barrel is a 9.125 or worse 10 twist! And to make it worse, the sub .25" group 107's won't let the bolt close in Remington 700 #3. (four letter words here)

Bullet stability isn't just about weight. It also involves the shape and length of the bullet.

 

[Rhett Crider]

Get some 105 HVLDs and go to town.

 

[Beelzebub]

Rather than relying on hearsay for what twist rate will stabilize a particular bullet, before you buy plug the figures into an online calculator.

JBM's calculator is here: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

If you need the length of the bullet for the calculation, you can get that from JBM also, here: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Plugging in the 110g Sierra Matchking (.243) with a bullet length of 1.335 inches and a velocity of 2,863 fps in a 1:8 twist barrel results in a stability factor of 1.248 at sea level. That's too low, in my book. I want to see at least 1.5 or above. FYI, the the 107g Sierra Matchking should stabilize in a 1:8 twist (stability factor above 1.5).

Last, you should manually check that new barrel's twist rate. It might not actually be 1:8.

No dang wonder they keyholed!

 

[Beelzebub]

Get some 105 HVLDs and go to town.

wind blowing, and wind not blowing

 

[Beelzebub]

Rather than relying on hearsay for what twist rate will stabilize a particular bullet, before you buy plug the figures into an online calculator.

JBM's calculator is here: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

If you need the length of the bullet for the calculation, you can get that from JBM also, here: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Plugging in the 110g Sierra Matchking (.243) with a bullet length of 1.335 inches and a velocity of 2,863 fps in a 1:8 twist barrel results in a stability factor of 1.248 at sea level. That's too low, in my book. I want to see at least 1.5 or above. FYI, the the 107g Sierra Matchking should stabilize in a 1:8 twist (stability factor above 1.5).

Last, you should manually check that new barrel's twist rate. It might not actually be 1:8.

Thanks Brother. It definitely isn't even close to n 8 twist. I drew as think a black line as I could down a fairly new cleaning rod set. Put a brand new .244/6mm brush on it, pushed it several inches into the muzzle and twisted the rod around to the 12 o'clock spot on the barrel and marked it. The handle was off the set of rods, so I used a piece of hard metal to push the rod further into the barrel. I tried to get it as close to "top dead center" as I could and marked it again. pushed the rod on down and through the barrel. Then I laid the first mark on the rod at the 0" mark of a metal yard stick. I repeated the borre measurement 2 more times with 2 different color markers. Black, Green and orange. All three measurements were within an eighth of an inch of each other. The ranged from 10 .24 to 10.450. So im guessing the barrel is probably a 10 twist.

 

[jebel]

No dang wonder they keyholed!

The ranged from 10 .24 to 10.450. So im guessing the barrel is probably a 10 twist.

Ouch! Sorry for that. You're going to need to come way down on bullet length (and weight). Maybe have some choice words with that A+ seller on Gunbroker as well.

 

[cornshank]

I've read many threads that say to stabilize a 6MM Sierra BTHP Match bullet you have to have an 8 twist barrel. I have a pair of old shot out Remington 700 243's in VLS. Both are 9.125" to 1 twist. Both will shoot the aforementioned bullet into a 3 shot one hole group at 100 yards. I have an RPR 243 with a 7.7:1 twist. It will shoot 10 shot groups under a half inch at 100 yards with the Berger 115 grain VLD Hunting bullet. SO I was wanting to shoot some of the higher BC Sierra 110 grain match bullets. My two old Remington barrels key-holed every one of them. So I looked and waited and looded and waited until I found what was advertised on GunBroker as a Remington Model 700 with a Lilja 8:1 twist barrel that hadn't been shot more than break in. seller was an A+ 4000+.

So this morning I boogied over to my new range to shoot this new/used rifle. Bore sighted it early this morning when I could see crosshairs and the lazer against the side of my white boat at 100 yards. Boat is in the back yard. I didn't haul it to the range ;-) Well, how disappointed was I when the first bullet in the target was a keyhole! And so were the next 9. The 110 grain bullets were seated a little longer to get a tad more powder in them safely and were actually 25 feet per second faster than the 107's With tail between my legs and my heart broken, I pee'd on the fire and called in the dogs and came home. So I guess I'll try the corn cob on stick trick and see if I can get a rough guess on the twist of this new rifle. BTW, the only markings anywhere on the barrel are 243.

Look at the bright side , at least you didn't shoot a hole in the boat!
Just kidding!

 

[Roughrice]

If he's A+ with 4000 positives... He would at least take it back or provide you a new barrel blank.
That was a big mistake on his part. That's not even close to an 8T.
I'm sorry for you brother.
That 10+ twist will not shoot your desired projectiles.

 

[HARPERC]

Maybe have some choice words with that A+ seller on Gunbroker as well.

More barrels are never measured than are. I have seen even quality custom barrels not be as advertised. One I shot for 30+ years that never failed me until the longer mono's appeared, and caused me to actually measure it.

Perhaps only lighter bullets were shot, with the barrel ordered as such in case the shooter wanted to have it in case heavier/longer bullets might be tried some day.

 

[BallisticsGuy]

What matters is bullet length. you could have a 87gr bullet but if it's 1.4" long you're going to need a much faster twist than you would with a 100gr bullet that's only 1.2" long. The spin has to be fast enough that the moment arm created is sufficient to counteract the desire of the bullet to go booty over teakettle. With long pointy bullets the center of gravity is well behind the middle of the bullet. The longer and pointier the worse the situation and the more spin needed to stabilize.