30-06 re barrel 1 in 10 or 12 twist ?

[Adk Mike]

I'm cast bullet shooter. I do not have a handle on this rifle twist stuff 1 in 10 or 1 in 12 etc. Is there a go to guide or rule of thumb so I can know the difference ?
I've got a Remington 725 I want to re barrel to 30-06 with a med barrel 24 inches long. Any thoughts ?

[oneokie]

If only cast and boolit weights 200 grain or lighter, the 12 twist will be the best choice.

[RPRNY]

http://www.ebr-inc.net/articles_Greenhill_Formula.html

As per above advice, for heavy cast at @ 2,000 - 2,250 MV, 1:12 will likely be your best bet.

[Larry Gibson]

The 12" twist will definitely be the best choice. If you are using cast up through 180 gr then you might consider a 14" twist and a 26" barrel. You can push 2600+ fps with excellent accuracy if that interests you.

Larry Gibson

[johnson1942]

i done the math what i use for all the guns ive built and this is what ive come up with. if you go 1/10 twist, a bullet that is 1.2 long will shoot to 200 yards very very accuratly but probably not good past 300 yards. a bullet 1.1 long will shoot to 1000 yards very well in a 1/10 twist. you could even go 1.05 long for 1000 yards. a 1/12 twist needs a bullet 1.1 long for accracy at its best to 200 yards. a .95 long bullet for 1000 yard shooting. this is cast boolit shooting and things can change if you go alot faster in copper clad bullets. i figured this for a .308 diam bullet. in castboolets keep to a blunter nosed bullet instead of pointed ones because at slower speeds they are more accurate. pointed bullets at slower speed have never preformed for me well and i even use a kieth nose design and it is really accurate. good luck and have fun

[Adk Mike]

Most of my cast shooting up to this point has been a US model 1917. I also have a Sears model 53 A in 30-06. My most common load is 13 of Unique with a 314299 or a 311041. Shoots good no recoil and a lot of fun. Original Battle sights on the 17 and a Lyman target sight on the Sears. This Remington will get a Lyman target sight also. One in 12 sounds like what I need. I can have a gunsmith friend install the barrel. Any thoughts where to get one ?

[country gent]

Shilen, douglas, lilja, pac-nor, harts, krieger, wilsons, all should have that barrel or make it. Obermeyers is now a part of Krieger from what I understand. Kriegers have a henry style rifleing that is supposed to be good with cast bullets. I have all the above on rifles and all have performed flawlessly. I thing to do is let the maker know what your planning and what you expect want to do and they can be very helpfull also.

[MaxJon]

The 12" twist will definitely be the best choice. If you are using cast up through 180 gr then you might consider a 14" twist and a 26" barrel. You can push 2600+ fps with excellent accuracy if that interests you.

Larry Gibson

I'm considering a 30-06 SS 12T x 26inch heavy barrel for 500m competition, for 180-190gn cast bullets. Do you think i should go 14T ?
Thanks

[vzerone]

No that's going to be 546.8 yards and that's a longs way to stabilize out a bullet that weight and length. I believe I'd go with a 12 twist.

If you're going to make a specific use rifle and put all the money into it, I'd use a match 30-06 reamer and I'd also want the throating made to specifications to the bullets you will be using. The standard 30-06 throat was designed for 220 grain bullets.

Do a lot of research before you commit.

[Texas by God]

What caliber is your Rem 725 now? They are a fairly scarce rifle ( basically a 721 with a US1917 safety) and unless your old barrel is bad maybe better left alone?

Sent from my SAMSUNG-SM-G930A using Tapatalk

[MaxJon]

Are you saying my 12T barrel won't shoot 185gn cast bullets accurately at 546yds?
I think it will shoot very well.

[Ballistics in Scotland]

Are you saying my 12T barrel won't shoot 185gn cast bullets accurately at 546yds?
I think it will shoot very well.

I'm just about sure that it will.

In a sense weight doesn't matter very much for bullet stabilisation. What does is length, density and shape. I'd consider 185gr. and 12in. doubtful with boat-tails or very long spire points, or with a material lighter than lead plus jacket. The main significance of the bullet being cast is that it is likely to be of an easily stabilised shape.

The twist required is inversely proportional to the square root of the bullet material, and directly proportional to the square root of the medium through which it passes. This has the interesting effect that a bullet fired in water, about 900 times the density of air, would require a twist 30 times as fast.

Normally satisfactory stabilisation is liable to break down at low velocity. But it is rotational velocity that counts. This doesn't decline nearly as fast as linear motion. A bullet which has lost most of its linear velocity at extreme range is usually still spinning fast enough to be stable. If you could watch a little spot marked on its exterior, you would see it travelling in a much tighter helix than it did at the muzzle.

Where a problem can arise is if you use reduced loads for practice or the elimination of backyard pests. If you half the linear velocity, you half the speed of rotation, and tumbling is extremely likely. This isn't the biggest of sacrifices, but it could let you in for buying a pistol mould.

So why prefer a slow twist over a fast one? There are three, or maybe it should be three and a half reasons. With cast bullets it reduces friction, and the possibility of leading. With a jacketed bullet driven at extreme velocities, it reduces the chances of core melting (frictional heat) and/or bullet disintegration (frictional heat and centrifugal force).

The third is that when a bullet is imperfectly balanced (which all of them are to some small extent), its centre of mass is actually travelling in an extremely tight helix while the bullet's exterior travels down that straight bore. On exiting the bore it obeys Newton's First Law by changing to straight-line motion - and that line is the last direction in which the helix was pointing. The better the bullet, the less this effect. But for a given bullet, the error increases with the faster pitch.

[Outpost75]

I can validate from my own experience what Larry says about a 14" twist in an '06. Interesting that even ordinary Ball M2 152-grain flatbased FMJ shoots much more accurately in the slow twist than it does in the 1:10". I can drive the 160-grain Harris design bullet to full jacketed velocity with IMR4064 with better accuracy than Ball M2 in the same rifle.

If you are adventurous and really want a high velocity cast bullet rifle, which will shoot accurately with 150-grain flatbased jacketed factory ammo for deer hunting, and be scary accurate with 160-grain cast bullets, as shown below, try a 15" or 16" twist barrel of target quality if you might luck into one. Otherwise I vote 1:14" unless your hunting situation requires heavy bullets for elk, etc. Then 12" is adequate.

Attachment 208695Attachment 208696Attachment 208697

[quail4jake]

What a great summary, is this all from Hatcher's Notebook or is there another source that you recommend for interior and exterior ballistics? And thanks!

[MostlyLeverGuns]

There are also several barrel makers that have 1-11 twist available.

[vzerone]

I can validate from my own experience what Larry says about a 14" twist in an '06. Interesting that even ordinary Ball M2 152-grain flatbased FMJ shoots much more accurately in the slow twist than it does in the 1:10". I can drive the 160-grain Harris design bullet to full jacketed velocity with IMR4064 with better accuracy than Ball M2 in the same rifle.

If you are adventurous and really want a high velocity cast bullet rifle, which will shoot accurately with 150-grain flatbased jacketed factory ammo for deer hunting, and be scary accurate with 160-grain cast bullets, as shown below, try a 15" or 16" twist barrel of target quality if you might luck into one. Otherwise I vote 1:14" unless your hunting situation requires heavy bullets for elk, etc. Then 12" is adequate.

Attachment 208695Attachment 208696Attachment 208697

What are you considering scary accurate and at what distance?

I find often that cast bullets shoot more accurate then jacketed (especially in the application of using a military rifle with original military ammo) is because you can fit the cast bullet to the barrel better. An example would be with the military bullet that isn't full groove size and loose in the throat.

[vzerone]

Are you saying my 12T barrel won't shoot 185gn cast bullets accurately at 546yds?
I think it will shoot very well.

Quite the opposite bullbarrel033, I'm saying it will shoot accurate.

[Larry Gibson]

I'm considering a 30-06 SS 12T x 26inch heavy barrel for 500m competition, for 180-190gn cast bullets. Do you think i should go 14T ?
Thanks

Stability is going to be based on the length of the bullet. A 311299 out of a 14" twist requires 1900 fps to be fully stabilized with a Sg of 1.4 (Sg of 1.4 means the bullet is fully stable but some accept a 1.3 Sg as stable enough) . The 311334 is about the longest standard cast bullet at 1.225" and it would need a 13" twist at 1960 fps for a Sg of 1.4. The MP 311-180 at 1.03", made expressly for the .308W, requires only 800 fps out of a 14" twist barrel for an Sg of 1.4.

If you consider jacketed bullets the Sierra 175 MK at 1.245" is barely stable at 2650 fps from the 14" twist yet it does very well at 1000 yards. The longer VLD type bullets require a faster twist such as 11 or 12". Most all FB'd jacketed bullets up through 180 gr are well stabilized by a 14" twist with practical jacketed bullet loads. All SPBT and HPBTs up through the 175 MK are also well stabilized.

Of course the slower 14" twist is best for cast bullets because the RPM stays under the RPM Threshold at 2600+ fps. A 31129 at 2400 fps will hold very well to 600 yards and farther.

[MaxJon]

The 12" twist will definitely be the best choice. If you are using cast up through 180 gr then you might consider a 14" twist and a 26" barrel. You can push 2600+ fps with excellent accuracy if that interests you.

Larry Gibson

What's your twist on this Larry?

[vzerone]

Stability is going to be based on the length of the bullet. A 311299 out of a 14" twist requires 1900 fps to be fully stabilized with a Sg of 1.4 (Sg of 1.4 means the bullet is fully stable but some accept a 1.3 Sg as stable enough) . The 311334 is about the longest standard cast bullet at 1.225" and it would need a 13" twist at 1960 fps for a Sg of 1.4. The MP 311-180 at 1.03", made expressly for the .308W, requires only 800 fps out of a 14" twist barrel for an Sg of 1.4.

If you consider jacketed bullets the Sierra 175 MK at 1.245" is barely stable at 2650 fps from the 14" twist yet it does very well at 1000 yards. The longer VLD type bullets require a faster twist such as 11 or 12". Most all FB'd jacketed bullets up through 180 gr are well stabilized by a 14" twist with practical jacketed bullet loads. All SPBT and HPBTs up through the 175 MK are also well stabilized.

Of course the slower 14" twist is best for cast bullets because the RPM stays under the RPM Threshold at 2600+ fps. A 31129 at 2400 fps will hold very well to 600 yards and farther.

That's why all the serious 1000 yard competitors use a 14 twist huh Larry? Explain this, most all the 30 calibers including the big magnums use a twist anywhere from 10 to 12. Why is that Larry if they are too fast a twist?