Using the recommended method from Chic on getting twist rate for a barrel it looks like my 30-06 has a 1 in 11 twist barrel. Does that sound right for a factory rifle? This leads me to believe my gun might do better with heavier bullets rather than the light ones. I have been shooting 150 factory loads for sighting, and yielded one .5" group, but now that I am looking at handloading, should I look at the 180's instead?

Red

In my experience most twist tables only list MIN. twist for a given weight.

More twist does not usually have a negative effect on anything but bad bullets. Spinning an out of balance bullet real fast is not apt to give much accuracy.

Super duper hotrod smallbores sometimes spin bullets too fast, causing them to fly apart. You will not be able to do this with an '06 and any sane load.

Shoot what works.
I have used 150 gr. Sierra MK's in my 300WSM, 1:10 twist, at over 3200 FPS without ANY sign that they do not like it.

Travis F.

Most factories use a 1-10 twist for the -06, as it is adiquate for the heavy bullets, but a few "varment specials" have been made with slower twists like 1-12.
Your 1-11 (if that is what it realy is) is slower and would normaly prefer a LIGHTER bullet than a standard 1-10.
FWIW my 1-12 30-06 prefers a 150gr bullet and is adiquate with a 165.
I'd work up a 150gr load as you already know that your rifle likes them, than try working up a 165gr or 180gr loadings.
Remember it's the length of the bullet that sets the twist rate, so a long slug (like the Nosler BT) will respond differently than a short bullet (say a Hornady RN) of the same weight. The longer the bullet the higher the RPM it needs to turn (RPM is a function of Twist rate and Muzzle velocity)

Go here, follow the instructions.


http://www.shortmags.org/shortmags/ref_data/TwistRateCalc.asp

I think your twist rate is a mistake, if truly 1/11"! The standard for .30/'06, as you probably know, is 1/10" (same as for the .30/40 Krag usiung 220 grain round-nose bullets of 4.5 calibers in length), but some have been made 1/12" to shoot bullets up to 150 grain weight more accurately than the faster twist is capable of.



There is a story from Springfield Armory of an instance in the early days of the 1903 Springfield when a particular run of rifles was showing unusual accuracy in testing after manufacture. Investigation as to why these guns were so accurate finally revealed that the rifling machine had "slipped a cog", and was cutting 1/11' twist barrels instead of the 1/10" twist that was the milspec. (Your 1/11" twist conforms to this finding!!) Well, the Army soon corrected this "problem", and had the machine back to making "correct" barrels quite soon, despite the fact that the "bad" ones shot better!



As you may know, required twist for any given bullet depends on the LENGTH of the bullet, rather than its' weight. The Greenhill formula will let you calculate if your twist is fast enough or not, but you must measure the length of the bullet to use it. This formula specifies that the required twist, IN CALIBERS, is equal to 150 divided by the length of the bullet IN CALIBERS.



Using this formula, I calculate that a .30 caliber bullet of 1.25" in length should be spun by a twist of 1/10.8", which should be close enough to your 1 in 11" twist to work. If you used no bullets that exceed 1.2" in length, you should be O.K., no matter what they weigh. Of course, a streamlined spitzer of this length would weigh quite a bit less than a blunt or round-nose slug of the same length.

Red, just fyi, there are still (European) manufacturers that make .30-06 barrels in 1-11. Blaser is one example, Sako another one. So, although the 1-10 is definitely more common these days, 1-11 is not unheard of. FWIW

- mike

I agree with Steve. However, Lilja states a 1-11" will stabalize up to 220 grains, and Shilen (if these names are uncommon to you, both Lilja and Shilen are barrel makers) states a 1-12" will stabalize up to 170 grains and a 1-10" up to 220 grains. I would lean more towards Shilen's estimates, and I believe you should be able to shoot a 180 grain bullet with success.

What none of the charts take into consideration is the MV. Sure a 1-12 will stabilize a 220gr IF it's being launched out of a 30-416 Rigby imp case running 65ksi, but it won't do it out of a 30-06 case (at least at sane pressures), because you can't get the FPS high enough. BTDT

I actually stated a 1-12" will stabilize up to 170 grains (stated by shilen), but yes, I did say Lilja states a 1-11" will stabilize a 220. I would agree though, I think you'd have to have very high MV to push the 220 from a 1-11", but how fast I don't know.