1:10" vs 1:12"

[Lone Hunter]

I use a 11.25 twist on my .308 win in FTR . I use Berger 185 Juggernauts with great results. Also use Sierra 175 MK’s too. Mainly shoot 500 - 1000 yds. Never shot anything heavier. 168 SMK’s shot great too. When I re barrel probably will go 1.10 twist. I can always turn down the magnification on a scope but I can’t turn it up if it’s not there.

 

[ISS]

In the end, it IS a personal choice; based on past anecdotal experience. But, I would rather have a bit of over spin and a slight loss of accuracy than under spin and risk missing the X or 10 ring at extended distance.

 

[Rob01]

Never seen a loss in accuracy going from a 12 to a 11 or 10. That’s an assumption being made here.

 

[FrankG]

A 12 twist will cover more then one thinks. A 180 and even a 190 grain
bullet can be stable. It's the length of the bullet and not the weight.

Here's a little exercise on JBM......Take a 180 SMK that has a length of 1.277".
Using a 12 twister with a speed of 2600 fps, your stable......I prefer myself
the least amount of twist for what the rifle will be used for......

12 twist won't shoot the 169SMK or the 177SMK either.

My twist rate calc for the 169's is a 11.02 min. twist. I have shot them thru my M14 with a 11 twist barrel on it and they shot pretty good and doing it with iron sights.

Shooting them out of my 10 twist M40a1 spec build... easy groups in the .3xx range.

Later, Frank
Bartlein Barrels

12 twist will handle most bullets up to 190gr. Again most bullets but not all.

I've shot plenty of 12 twist barrels, 11.25 twist, 11 twist, 10 twist and 8 twist barrels in 308win.

From now on... just running 10 twist barrels.

 

[Rob01]

12 twist won't shoot the 169SMK or the 177SMK either.

My twist rate calc for the 169's is a 11.02 min. twist. I have shot them thru my M14 with a 11 twist barrel on it and they shot pretty good and doing it with iron sights.

Shooting them out of my 10 twist M40a1 spec build... easy groups in the .3xx range.

Later, Frank
Bartlein Barrels

12 twist will handle most bullets up to 190gr. Again most bullets but not all.

I've shot plenty of 12 twist barrels, 11.25 twist, 11 twist, 10 twist and 8 twist barrels in 308win.

From now on... just running 10 twist barrels.

Ah what do you know!

 

[Fuj]

12 twist won't shoot the 169SMK or the 177SMK either.

Later, Frank
Bartlein Barrels

Sorry Frank but totally disagree My other caculators show they will, and so
does my Hart 6 groove barrels. My favorite is the Hart 12 twister......I run the
!75's at 2700 fps in my M-70 Winchester, 26" Hart. It's more then stable enough.
For what it's worth (which doesn't matter) It's not a .308 but my catted 30/284.

 

[FrankG]

Sorry Frank but totally disagree My other caculators show they will, and so
does my Hart 6 groove barrels. My favorite is the Hart 12 twister......I run the
!75's at 2700 fps in my M-70 Winchester, 26" Hart. It's more then stable enough.
For what it's worth (which doesn't matter) It's not a .308 but my catted 30/284.

The 175SMK will stabilize in a 12 twist. No disagreement there.

The 169SMK is on the ragged edge of being stable in a 12 twist and even if they do you might be compromising the BC of the bullet. The 175 Sierra TMK's are longer yet and need a min. twist of 11.396.

If the bullets BC gets compromised even if it's here or there...your groups will suffer. Why run it on the ragged edge?

Both of those bullets are longer than the standard 175SMK.

That's based on 2600fps. If you can run them faster... your golden but if you cannot hit those velocities and you come in a little slower... performance will suffer.

 

[Desert Fox]

12 Twist PacNor 3 grove Supermatch

 

[Acyr]

National FTR records have been set with 185 Juggs in a 12 twist. National FTR championships have been won with 200 Bergers in a 11 twist. Speed matters. There are no absolutes in shooting long range. 10 twist is the easy button though.

 

[PH]

My .308 has a 14“ twist for 300m competition. 125 Sierra flat base green tip.

 

[charlie b]

Yep, vel and bullet shape/construction/length matter.

Keep in mind some of the Palma folks are running longer barrels and hot loads to get the speed up, so a 12twist in one of those long tubes might work but in a 20" barrel it might not. Then there is the effect of really cold weather that can mess things up.

I had a 10twist but wanted slower for my cast bullet shooting. 12 to 14 twist would have allowed a higher MV without rotational issues. But, I can't cast anymore so it's a moot point.

 

[drop_point]

Choose based on the purpose of the gun. I would go with something very different for a sporter hunting rifle vs an FTR rifle, for instance. I have hunting guns with 1:12" that are fine for that. But I would go 1:9 or 1:10 to shoot 200.20X Bergers for F-class.

 

[Coyotefurharvester]

I would go 10 for hunting rifle that you may/need to shoot lead free bullets.

 

[David Milisock]

My Palma rifle is a 1-12T and I shoot 155 n 185 gr bullets. The 185 s shoot well at 1000 yds.
1-10T is the norm if bullets over 180-190 gr. are in the mix.

What barrel length and bullet velocities, please?

 

[Bob3700]

What barrel length and bullet velocities, please?

My Bartline bbl is a 5R 12T 32" in length. 155's will exit at 2950-3000 fps. The 185 Bergers will achieve 2760 fps or so. Both will easily make 1K. I use Varget or VV140 with the 155's and VV150 with the 185's.

 

[David Milisock]

My Bartline bbl is a 5R 12T 32" in length. 155's will exit at 2950-3000 fps. The 185 Bergers will achieve 2760 fps or so. Both will easily make 1K. I use Varget or VV140 with the 155's and VV150 with the 185's.

Thanks makes sense!