OzFclass

Frank Green wrote:To fast a twist? I tell everyone this......I error on the faster side of the twist than vs. running the twist on the ragged edge of being stable. Being on the ragged edge of being stable if you shoot at different elevations, temperatures etc...you can run into stability problems.

To fast a twist can give you accuracy problems but this is usually linked to to much run out in your bullet/loaded ammo or shooting a poor quality bullet. A poor quality bullet or ammo with excessive run out the faster twist will amplify the run out. This is caused by the bullet not starting more in a true center line of the bore of the barrel. The more run out and when the bullet makes the jump to the rifling the more of a premature the wobble is going to be from the faster twist.

If your shooting good quality bullets/ammo with little run out I don't see a faster twist being a negative thing then.

You have to start the twist rate needed based on the longest/heaviest bullet you intend to shoot.

The number of grooves in my opinion has no bearing on accuracy or barrel life. I do believe though the 5R style rifling does help fight bullet failure. The lands don't directly oppose one another and in conjunction with the angles on the sides of the lands the 5R will distort/upset the bullet jacket less.

Later, Frank
Bartlein Barrels

Mr Green is absolutely correct.
I have fitted many 10" twist barrels for 155 Palma style bullets in .308, at least 4 Queens Prizes have been won with these. The range of bullets you want to shoot 12" twist will work well, but I would use a 10" twist for myself.
Keith H.

Pommy Chris wrote:

Frank Green wrote:To fast a twist? I tell everyone this......I error on the faster side of the twist than vs. running the twist on the ragged edge of being stable. Being on the ragged edge of being stable if you shoot at different elevations, temperatures etc...you can run into stability problems.

To fast a twist can give you accuracy problems but this is usually linked to to much run out in your bullet/loaded ammo or shooting a poor quality bullet. A poor quality bullet or ammo with excessive run out the faster twist will amplify the run out. This is caused by the bullet not starting more in a true center line of the bore of the barrel. The more run out and when the bullet makes the jump to the rifling the more of a premature the wobble is going to be from the faster twist.

If your shooting good quality bullets/ammo with little run out I don't see a faster twist being a negative thing then.

You have to start the twist rate needed based on the longest/heaviest bullet you intend to shoot.

The number of grooves in my opinion has no bearing on accuracy or barrel life. I do believe though the 5R style rifling does help fight bullet failure. The lands don't directly oppose one another and in conjunction with the angles on the sides of the lands the 5R will distort/upset the bullet jacket less.

Later, Frank
Bartlein Barrels

Thanks Frank,
So for a rifle that I want to shoot 185 hybrids in and maybe 155 hybrids what twist would you choose?
I ordered the 4 groove barrels for now as it is all I can get but I do want to get another barrel.
Cheers
Chris

Chris, Shot 4 groove barrels for years. Nothing against them. Most of my .308win. type guns I'm running a 1-11 or a 1-11.25 twist. Most of the bullets I shoot are 155 Lapua's (those will fly out of a 1-13 twist barrel with no problem) and back ups are 175 Sierra's and 168 Hornady Amax bullets.

Very first barrel we made for testing was a .30cal., 4 groove, 1-10 twist. I chambered it in .308win./obermeyer chamber reamer. Shot 175gr. Sierra's thru it. No break in etc...shot 50 consecutive rounds thru it with out cleaning. Last group off the bench at 200 yards was a 1/4".

Up to a conventional 190gr. bullet will fly in a 1-12 twist but I feel the heavy 185/190gr. bullets are at the ragged edge in a 1-12 barrel. I would prefer a 1-11 or a 1-10 twist barrel.

My thinking and wisdom is being changed somewhat at the time. Very popular with the 215gr. bullets for FTR shooters over here is a 1-9 twist over a 1-10. Also with testing our military is doing with fast twist barrels in .30cal. and 6.5mm I'm leaning towards faster twist for extended ranges.

Just remember a fast twist barrel if you have crappy ammo with a lot of run out/poor bullet quality a faster twist will amplify the wobble and you can see worse groups. Stick to good components/ammo and I don't feel you will see a problem.

If you ask me flat out 185gr. bullets in a .308win. I would go 1-10 twist.

Later, Frank
Bartlein Barrels

Frank Green wrote:

Pommy Chris wrote:

Frank Green wrote:To fast a twist? I tell everyone this......I error on the faster side of the twist than vs. running the twist on the ragged edge of being stable. Being on the ragged edge of being stable if you shoot at different elevations, temperatures etc...you can run into stability problems.

To fast a twist can give you accuracy problems but this is usually linked to to much run out in your bullet/loaded ammo or shooting a poor quality bullet. A poor quality bullet or ammo with excessive run out the faster twist will amplify the run out. This is caused by the bullet not starting more in a true center line of the bore of the barrel. The more run out and when the bullet makes the jump to the rifling the more of a premature the wobble is going to be from the faster twist.

If your shooting good quality bullets/ammo with little run out I don't see a faster twist being a negative thing then.

You have to start the twist rate needed based on the longest/heaviest bullet you intend to shoot.

The number of grooves in my opinion has no bearing on accuracy or barrel life. I do believe though the 5R style rifling does help fight bullet failure. The lands don't directly oppose one another and in conjunction with the angles on the sides of the lands the 5R will distort/upset the bullet jacket less.

Later, Frank
Bartlein Barrels

Thanks Frank,
So for a rifle that I want to shoot 185 hybrids in and maybe 155 hybrids what twist would you choose?
I ordered the 4 groove barrels for now as it is all I can get but I do want to get another barrel.
Cheers
Chris

Chris, Shot 4 groove barrels for years. Nothing against them. Most of my .308win. type guns I'm running a 1-11 or a 1-11.25 twist. Most of the bullets I shoot are 155 Lapua's (those will fly out of a 1-13 twist barrel with no problem) and back ups are 175 Sierra's and 168 Hornady Amax bullets.

Very first barrel we made for testing was a .30cal., 4 groove, 1-10 twist. I chambered it in .308win./obermeyer chamber reamer. Shot 175gr. Sierra's thru it. No break in etc...shot 50 consecutive rounds thru it with out cleaning. Last group off the bench at 200 yards was a 1/4".

Up to a conventional 190gr. bullet will fly in a 1-12 twist but I feel the heavy 185/190gr. bullets are at the ragged edge in a 1-12 barrel. I would prefer a 1-11 or a 1-10 twist barrel.

My thinking and wisdom is being changed somewhat at the time. Very popular with the 215gr. bullets for FTR shooters over here is a 1-9 twist over a 1-10. Also with testing our military is doing with fast twist barrels in .30cal. and 6.5mm I'm leaning towards faster twist for extended ranges.

Just remember a fast twist barrel if you have crappy ammo with a lot of run out/poor bullet quality a faster twist will amplify the wobble and you can see worse groups. Stick to good components/ammo and I don't feel you will see a problem.

If you ask me flat out 185gr. bullets in a .308win. I would go 1-10 twist.

Later, Frank
Bartlein Barrels

Thanks Frank,
My 1 in 10 barrels should arrive tomorrow or the next day so I can get them fitted soon good to hear the 1 in 10's should be fine. I shoot 155 hybrids so I am planning to shoot the hybrid 185's, for FTR probably most of the time so the 1 in 10 seems a good match. I really want to screw out my Border though as it is a nail driver, not the perfect twist but 7 x's in wind on Sunday (59 with 7) dont ask about the 5..
Chris

Good info all round on twist rates. Following on from that what length barrels are required for 155-185s to ensure you have enough for the longer ranges???

Dee Cee, one of a series of test barrels used with factory ammunition in a 1-14 twist, assuming this setup was similar to yours performed best at 29 inches at 1000 thousand yards. Other barrels which were tested included 12, and 1-13. Better results were attained at 31.5 inches at one thousand yards. The thing that you may not know is that short barrels about 21 -26 inches a rule of thumb is, an extra inch in length will add 30 fps. In the longer barrels the marginal benefit decreases significantly and you may only be adding 10-15 fps per inch.