Last week I purchased a CZ 550 30-06 which the factory has the twist listed at 1-12” I believe. I’ve been pondering the slower twist when the topic of twist came up on this forum a few days ago.

I guess, for the most part, I’ve been a ‘heavy bullet for caliber’ kind of guy. I’ve mostly used 180s and have tried 200s in my previous 06s, though 165s generally seemed more accurate in their 1-10” twists.

Does anybody have experience with this caliber and twist, or suggestions?

Thanks,
Jim

Although I don't have any personal experience with the'06 with a 1-12 twist, I have friends who have them, and I have other 1-12 twist rifles.
Think of yourself now as a light weight bullet guy.. Not trying to be a smart ass, but 1-12 twist and light weight bullets go hand in hand.
I'd think 150 grain bullets and below would work well.
But, there may be other guys who will post here who do have personal experience and give you the straight skinny on what does shoot.
I do know that a 1-12 twist 308, in a good barrel, is hugely accurate with 130 grain bullets.

Don

A 12 twist will work with 190 grain bullets on down to the lighter weight ones.

The 1-12 twist is sufficient for most .30 caliber hunting bullets. Weatherby used it for their .300 WBY rifles for many years, and those typically used ammunition with a 180 grain or heavier bullet. I doubt your having any trouble with anything up to a 200 grain spitzer of conventional construction or a 220 grain RN. Heavy monometal bullets or other longer-than-standard bullets might give you trouble.

LEt me point out that most 308/7.62NATO target rifles which are shot out to 800 & 1000yards are typically built with 1:12" barrels and are intended to shoot 180gr and 190gr match bullets.

You'll be FINE with a 1:12

Infact the rifle will likely be more accurate with the 165's.

AD

How much twist you need depends on bullet length, and velocity.

A very long 180gr might need more twist than a 220gr RN.

With most 30-06 hunting loads at hunting distances you should be fine.

Many 308 rifles have 1 in 12 twist barrels and work very good with 180gr hunting bullets.

I looked at the Shilen barrel website and checked their twist rate rocommendation and with a 1/12" .308 bore they say 170 grains or less. I have found Shilen's twist information to be spot on and consider them experts in the industry.

If you shoot copper monometal bullets, you are limited to no heavier than 140gr if it is a boat tail bullet. Heavier monos will shoot accurately but terminal failures will increase, as the length increases over 140gr.

I see all their 30 cal rifles are 1:12" twist now. That is a pity because one could still live with a 30-06 in 12" but a 300 WM in 1:12" is very limited.

I have a very accurate Rem 700 Police in .308 Win. I was told that the 1-12" twist was meant for the 168 MK bullet. As a matter of fact, 168-175 match bullets seem to be the standard among sniper circles.


This being said, I own another target rifle in .308 Win with a Lothar Walther 1-10" bbl. and honestly can't see any difference vs. the 12" twist.

Or you can consider some excellent bullets like Norma Oryx 200 gr. or Lapua Mega 200 gr. that are shorter than spitzers; remember that the bullet lenght counts more than weight in term of stabilization. The Oryx is a slightly better bullet, though.

quote:

Originally posted by Andre Mertens:
I have a very accurate Rem 700 Police in .308 Win. I was told that the 1-12" twist was meant for the 168 MK bullet. .....

I have a 1:12 308, too. It shoots 165 SGKs accurately.

I don't have any experince with 168 SMKs but have also read where they are designed to be the longest bullet that a 1:12 308 barrel twist will stablize to 1,000 yds. That's why they have such an odd weight - They are not designed to wt. but to length!

Those 165 SGKs I use are 1.18" long. When run through the Greenhill formula, It predicts that a 1:12 twist just stablizes this bullet below 2,800 fps. So that agrees well with what we have heard/read and what Sierra designed.

So...for a 1:12 30/06 I'd say your are safe to assume that it will stablize bullets 1.2" or shorter.

This should cover 130s, 150s and most 165s. It would also cover some 180s if the nose was blount enough to have a length 1.2" or below. Can't say w/o a measurement, but suspect 200s could be to long.


PS: Now remember, just because a bullet is spun fast enough to stablize it - DOESN"T mean that particular rifle will like it!

I spent years shooting the national match course out to 600 yards with M70 Win and M1A in .308 with 1 in 12 twist. They shot great with bullets as heavy as 190 gr Sierra Match AS LONG AS THE THROAT AND MUZZLE CROWN WHERE NEW AND NEAR PERFECT. The standard rifling twist for any caliber has a little "fat" in it so that it will still stabilize the greater initial yaw caused by a less than perfect barrel condition. With a 1 in 12 30 cal with bullets over about 170 gr, you have no fat. So the accuracy life will be less. Most guys that shot "accross the course" with me would switch to a 1 in 11 or 1 in 10 .308 barrel after the original barrel wore out.

For 150 gr or 165 ge 1 in 12 is fine, even with a little wear. A 1 in 12 will shoot 190 gr as well as any barrel WHEN IT IS NEW IF PROPERLY CROWNED.

Brazos Jack

In a Remington Varmint 1 in 12 308 I got very good accuracy with the old long boat tail Sierra 180 MK and the 190 MK when I shot Metallic Silhoutte. We only shot to 500 Meters.

The Federal factory Match load with the Sierra 168 MK will not always stay super sonic to 1000 yards.

Since Sierra changed the boattail of the 180MK it will not either.

This is the main reason for the 175MK. The Federal Match 175 MK will usually stay super sonic to 1000. It usually shoots good in 1 in 12 barrels.

In most guns it is not as accurate on paper out to 600 yards as Federal factory 168.

I have also shot and seen a fair amount of the old Military 172gr FMJ Match shot in 1 in 12 Remingtons.

It never shot as good on paper as 168 Federal Match out to 800 yards.

It always shot better at 1000 as it always stayed super sonic.

After Sierra changed the boattail on the 180 MK, many did not want to shoot 190 MK's in their M1A's, so we shot the Sierra 180gr Game king, as they did not change the long boattail shae on that bullet, at least back then, I have not bought any of them lately.

Those 180 Gamekings shot VERY good.

quote:

Does anybody have experience with this caliber and twist, or suggestions?

Around 1976 as I recall, I had an FN commercial mauser with a bad barrel rebarreled with a 1 in 12" Douglas barrel, caliber 30-06. That rifle will put 5 220 gr. Sierra round nose Pro-Hunters into a group slightly under one inch whan I do my part. I now have to work up a different load as the powder I then used has been discontinued. velocity was, as I recall 2450 FPS from the 24" barrel.
As an aside, I shoot that same bullet from a Winchester M70 in .308 Win. with the 1 in 12" trist at 2310 FPS and groups run from .375" to .50" most of the time and the worst group was on a windy day and it was still one inch.
JMHO, but anyone that says you can't shoot a 220 gr. bullet from an 06 accurately with a 1 in 12" twist is full of bull, at least shooting the round nose bullet. I've never tried a boat tail bullet mainly because I just don't like them. personal prejudice and nothing more.
Paul B.

Back before I knew anything about barrel twist, I had a 308 that shot 180 gr factory ammo really well. Now that I reload and know that the twist of that rifle is 1-12, I think it is "supposed" to shoot 125 grainers. It is very accurate with these as well. But I've actually caught myself thinking that it won't shoot well with 180 grain bullets because of the twist. Experience tells me the contrary. Point is, DO NOT overthink it. Try it!

A lot depends on whether you are going to shoot paper or hunt with the rifle. If it is going to be paper only, bullets with a stability factor as low as 1.1 will give round holes on paper most of the time.

Hunting requires a higher s/f for reliability. Depends on what you want to do.

/

When a bullet transitions from flight to tissue, especially if it arrives at a steep angle of incidence, it needs a stability factor of at least 1.3 (1.4 or higher is preferable) to make the transition without getting sideways. Once the transition is made and it has been done without excessive yaw (during transition), stability factor becomes a non issue. Other parameters determine how deep and in what manner the bullet will penetrate. A bullet that swings the tail on impact has little chance after that.

We proved this again recently.

1. A customer with a 1:12" twist Sauer 90 in 30-06, used 150gr HV bullets on a number of animals and observed much meat damage. We switched him to 130gr HVs going 150fps faster and linear penetration improved and meat damage reduced on all 5 animals shot thus far.

2. A customer with a 300WM, built on a former bisley shooting barrel with a 1:11.5" twist, shot an eland with our new 140gr HV developed for 1:11" Blaser 30cal and the new 1:11" 30cal Sako rifles. He took a 7 o'clock shot, entered on the last rib, broke two ribs, penetrated straight in just inside the rib cage and lost the bullet in the front of the chest somewhere. The same shot with a 160gr HV on smaller animals produces curved trajectories in the animal and sometimes a tumbling bullet.

This is no longer a question about which I lose any sleep. It is my observation of the last ten years of building expanding monos. If the stability factor is below 1.3 with a mono, unpredictable things happen. Get it over 1.4 at impact and reliability results. I am only interested in reliable, repeatable performance.

Can't buy Gerard's explanation.

If a bullet is marginally stable at, say 70F temperature, it may not be at 25F. Also, a SF of 1.1 requires a very good bore and crown to keep the initial yaw low enough as the bullet exits the muzzle for such a low SF to stabilize.

However, no bullet will be remain gyroscopically stable in a medium substantially denser than air, like tissue. Once no longer gyroscopically stable it will want to travel heavy end forward like a badmitten cock or a hollow base shotgun slug. For parallel sided round nose bullets or those that mushroom into a shape that is decidedly heavy end forward, this isn't much of a problem. But a spire point definitely would prefer to travel butt end forward once it loses gyroscopic stability. Some are just a bit faster than others about making the transition. If a spitzer bullet yaws in tissue before it has had time to mushroom and then breaks up when the stress of traveling sideways exceeds its mechanical strength, the the tissue damage will be considerable. This is what happens when an M-16 bullet strikes with an impact velocity of at least 2500 fps (out to about 130 yards). Making this happen faster in flesh is why the British put a light weight wood or aluminum front core section in their Mk VII .303 loads in WWII.

So you cannot convince me that any normal rifling twist will be decernably different in how fast it yaws in tissue, provided it was stable and point forward when it struck.

You can convince me that a bullet that was marginally sable, but stable none the less, on the warm summer day when you sighted in might show considerable yaw before impact on a cold winter day in the hunting field, leading to it yawing to the failure point after impact before it could mushroom and leading to the observation you describe.

All of this aside, marginally stable barrels are a pain. It will only take a bit of crown wear to ruin its accuracy leading to half or less the accurate barrel life of an appropriate twist and, if right on the line, then even a minor temperature drop can land you in the soup, as the U.S. Gov't found out when it field tested the early 1 in 14" twist M-16's in Alaska. So for an '06 I would definitely recommend the std 1 in 10" if you want to use the full range of bullets up to 220 grain. If its going to be strictly a deer and antelope rifle using 150 gr max then 1 in 12" is more than adequate. 1 in 12" will only stabilize long 180 gr + bullets when everything is otherwise in very good shape. A worn crown combined with a cold day and you're in the soup.

Slower twist barrels wear more slowly, build up jacket metal fouling more slowly and generate less chamber pressure at a given velocity level. But a barrel with a reasonable conservative SF will shoot well longer and in more varied conditions than one with a marginal SF. So be reasonably conservative, just don't get silly about it and think "if a little is good, more is better, and too much is just enough". A 1 in 8" or 9" .30-06 would have no advantage over 1 in 10" with existing projectiles and would have several disadvantages.

Brazos Jack

What a neatly informative thread!! roger

The short answer to the OP is this:

1-13, 1-12, 1-11, 1-10 will all work for a hunting rifle using 200 grain bullets and under. If shooting this rifle like most do with a hunting rifle, the barrel will outlast you.

You'll be fine. Unless of course you plan on shooting 200 grain bullets at 800 yards all the time, then I'd opt for a faster twist.

I'd say a 180 is the most popular weight for the 30.06. Your twelve twist is just about perfect.

/

The requirement of twist rate / bullet length is different for target shooting beyond 500m and not relevant to hunting closer than 500m.

quote:

There is no indication that the wounds between the same bullet fired from a 1:10 twist would be any different to a 1:14 inch twist at 600 yards.

This is because the stability factor has increased at that distance so that both twist rates deliver sufficient stability for good transition from flight to tissue. Try the same thing with a 180gr mono at 100 and you will quickly see the difference in terminal performance. The 1:10" twist will be better than the slow twist enough times that it will be noticed.

However, a 180gr match bullet from a 1:13" twist will be preferable for punching paper at 1000 compared to a 1:10" twist, not so?

quote:

the reason you put forth if I understand your narrative is that one bullet " is more stable than the other" based on SF number; this does not jive.

quote:

Thus they become more stable as velocity drops off and "more stable" as angular velocity increases.

You contradict yourself, I dont understand your reasoning.

There's a tale in Hatcher's Notebook concerning a batch of .30/'06 barrels made at Springfield that were rifled 1/11" by mistake once. The clue to the malfunction was the fact that the guns were all more accurate than the ones rifled with the standard twist of 1/10".

The offending rifling machine was duly "corrected".

Any anomaly in the jacket or core of a bimetal bullet will be enhanced by tighter twist. That is why one weighs lead core bullets - the weight discrepancy of a bad bullet will point it out. Bench rest shooters will use the slowest twist that will give acceptable stabilisation and no more - to minimise the effect of tighter twist rates on non concentric jackets or cores.

As long as you shoot paper for accuracy alone, it should not be any other way. Hunting has a different requirement - good terminal ballistics and this is enhanced with tighter twist rates.

Turned monos of course do not suffer the anomalies of non concentric jackets and cores - they don't have such things.

I have shot thousands of rounds through my 30-06 Husqvarnas that have 1-12" factory barrels. They had no problem shooting sub 1" with 180 gr. loads they liked. I had limited experience with 200 gr. loads, but there was no sign of bullet instability.

/

I am not sure about meat damage, but it seemed to me that a 270 WIN. with 1/9" twist killed exceptionally well, perhaps better than one with a 1/10" twist.

/

quote:

The yaw of repose of a 30 cal Sierra match bullet for a 1:10 , 1:12 and 1:14 inch barrel at 300 m is something like 0.015 deg , 0.014 and 0.013 degree.

These differences are amazingly small - .001 or 1/1000th of a degree at each interval. This is minute !!!

Warrior

I just orderd a 1-12 30-06 just to test and see if it makes any differenace.

Will post results later.

Terry,

How would you test, ie your methodology?
What bullet weights or just one specific weight?
Curious to know.
Thanks
Warrior

I will try 150 gr on up to 220 just to see if any keyhole, and just want to see if any particular bullet weight shoots better or worse than my "normal" 1-10 twist 30-06's.

quote:

Originally posted by Terry Blauwkamp:
I will try 150 gr on up to 220 just to see if any keyhole, and just want to see if any particular bullet weight shoots better or worse than my "normal" 1-10 twist 30-06's.

I have fired 220 grain RN bullets in my 1/12" twist .308 pre-64 M70 at 2200 FPS with good accuracy results. These were over 4 calibers in length.

I really doubt if I will see any differance at all in performance with the 1-12.

quote:

Originally posted by ALF:
I did a search of articles that deal with impact condition of the bullet specifically in terms of the reltationship between yaw at time of impact and the length of the narrow channel in the target and came up with the following:

There is definitely a relationship between yaw angle at impact and the length of the narrow channel, that is not disputed ! and it reinforces that for non deforming, non frangible bullets at least all things equal that narrow channel length would only be a function of the bullet's physical dimension as it pertains to mass distribution. ie the bullets axial and longitudinal moments of inertia.

The question therefore is what is the difference in yaw of repose of say a 30 cal bullet fired at same velocities from a 1:10, 1:12 and 1:14 barrel at hunting distances say at 200 m and at 300m. (We are assuming off course bullets that are symmetrical)

Fact is that the yaw of repose values at 200 and 300 m are very small, measured in 100ths of a degree and the difference at 200 and or 300 m between a 1:10 1:12 and 1:14 inch twist barrel is so small that it would have no significant impact Length of narrow channel at all.

The yaw of repose of a 30 cal Sierra match bullet for a 1:10 , 1:12 and 1:14 inch barrel at 300 m is something like 0.015 deg , 0.014 and 0.013 degree. For practical purposes it would not amount to measurable difference in distance it would take any of these bullets to turn inside the target and hence there would be no difference in wound profiles between these twist rates.

Hey alf, I'm not sure I follow what you are getting at. Any chance you could "explain" that post a bit more?

Hot Core,

Just in clarification of your question; would you like Alf to give the formula and show the calculations and answer of each for the yaw of repose OR to give a non quantitative description of the logic without repeating what he has said before?

http://www.fulton-armory.com/fly/yawrepf.htm

What is your view on this matter? Perhaps you could also touch on the condition when a bullet flies with it nose up from its trajectory path:

A) what causes this condition, and
b) what could happen when the bullet hits the target

Warrior

Any and all the above. Trying to read through alf's post tended to confuse the issue. Just looking to see if "alf" can clarify anything he posted.

I'd rather listen than join in the discussion, but thanks anyhow.

/