Home Forums Hunting & Shooting Ask The Gunwriters Twist Rate

Most 30 calibers are 1-10, Sako's are 1-11. What is the reason for this?

Now which model rifle are you talking about.

The reason for the different twist rate is probably due to the length of the barrel used and the projectile it is designed to propel.

Length, weight and shape of projectile determines which twist rate might work best. Using the Greenhill formula - the equasion for a bullet traveling at about 2800 fps - which is a fast round for the 30-06 - the result is a twist rate of about 10.9 for a 150 gr. / 30 caliber bullet.

Since the SAKO engineers knows this - it is probably reasonable for us to assume that this is going to be about the fastest that a 30-06 bullet is going to travel down their barrel - so it is probably the determining factor as to where they set their twist rate for their barrels.

The reason why I use 30-06 is because the 30-06 is the round by which all other rounds are measured.

Twist rates are determined by the manufacturer for the speed and size of the projectile that comes out of the barrel. Hence a faster bullet would need more stability then a slower moving round.

The heavier the bullet the slower it usually travels through a 30-06 type gun and the less gyroscopic it is - due to the fact that the bullet tends to be rear heavy and falls out of suspension easier and is more susceptible to yaw and tumble.

One other fact is that the slower twist rate barrel lasts longer then the faster twist rate barrel - due to the fact that barrel will wear faster with a faster twist rate - throat erosion occurs faster and when the barrel wears out - the accuracy will suffer.

That is the reason why the .220 Swift barrels never lasted very long compared to a .30-06...

Because other makers used a 1-12....and some malarky thrown in.

Duquesnebeer,

Once again you are full of BS on several points.

The reason that some .30-06 barrels have a 1-11 twist is that it's been found to be more accurate with many bullets, especially longer match spitzers in the 190-grain class.

The Greenhill formula was not designed for bullets "traveling at about 2800 fps". It was designed back in the days of lead bullets traveling at under 2000 fps. It has some simplistic applications for faster jacketed bullets, but there are many better formulas today.

A typical 150-grain .30 caliber spitzer started at 2800 only requires about a 1-16" twist, even a very long bullet such as a boattail match bullet.

Bulets that are "rear heavy" actually tend to stabilize better than bullets with a center of mass toward the front. This is one reason match bullets usually have very long hollow-points with a core that doesn't reach all the way to the tip.

The rate of twist has realtively little to do with how long a barrel lasts. The big factor is how much gas is being pushed through a small hole. The typical .220 Swift twist is 1-14, rather than 1-10 as in the .30-06. The reason Swift barrels burn out quicker is that hot gas is being pushed through a small hole.

I don't know whether you are a troll or simply ignorant. I am starting to bet on the former, but who knows?

Now, that's some serious horse puckey, right there.

"...fall out of suspension..."???

Jeezus......

Actually, I am beginning to guess troll, though a really odd variety. Our new friend Duquesnebeer apparently never returns to a thread he posts on. He just posts once, with all sorts of of BS, then hits another thread, again with a single post.

A very different technique than most trolls.

I am just trying to understand, does the 11 twist generally do better with one weight/length of bullet and the 10 twist with another. My sako (1-11) really likes the 168grTSX but opens groups up to 2" with a 200 gr AB. Other AB's in other calibers/weights have proven real accurate for me. or is there something else at play here effecting accuracy?

I think you give him too much credit calling it a technique. I think Attention Deficit Disorder is more likely.

What caliber? How much velocity are you getting with the 200 AB's?

That is exactly what I was thinking only I used a slightly more harsh term than horse puckey

What caliber? How much velocity are you getting with the 200 AB's?[/quote]

getting 2625fps with a 200gr AB outa a 3006 the 168's run 2900fps

Is your barrel a 1 in 10 twist?

As long as the twist rate is fast enough to achieve stability with a given bullet length, it doesn't really matter. A ten inch twist will stabilize a longer bullet than will a twelve but that doesn't necessarily mean it will shoot a longer bullet better than a short one.
I have been told that an excessively fast twist may cause the bullet to maintain the same attitude as when it left the barrel and it will, as a consequence, oscillate at long range. I can not dispute this since I've not observed a bullet in flight at long range (at least not well enough to determine it's attitude).
The 11 inch twist on the Sako might atually be a 28 cm twist or something and they make that twist just because they want to. I have a Swiss barrel which measures 26cm for twist. In the field, the difference between a ten inch twist and an eleven inch twist will not be noticable with any bullets one is likely to use. GD

You're consistant, I'll give ya that. It doesn't matter the subject either.