what twist do you recommend for a 30-06?
That's really going to depend on what bullets and what you want to shoot. Most anything and everything above 168gr. weight works great at 1k If your going with the 155gr like the Palma type bullets that something else, it all about speed there.
Here's a piece of information that might help you.
Twist Rate - The standard rate of twist for factory and arsenal barrels chambered in .30-06 is 1:10". This was established in 1903 with the .30-03 cartridge that used the Krag's 220 gr. round-nose bullet at a very modest muzzle velocity. As the cartridge evolved into the .30-06 with a 150 gr. spitzer bullet, the original rifles had their barrels set back and rechambered with the new short-throat chamber for the lighter bullet, but naturally the rate of twist remained the same. That's ancient history and we don't need to repeat it; what we need is the optimal rate of twist for modern match bullets, and that is the 1:11" twist. This will properly stabilize bullets up to 210 gr. with no concerns and that's as heavy as we're going to consider in this series.
As a fundamental rule, the slower you spin a bullet the more accurate it can be. The reason is simply that bullet jackets aren't perfectly uniform in thickness and a slower rate of spin keeps those tiny variances from altering the bullet's flight. Think of a car tire with a slight imbalance, the faster you go, the more you feel that thumping. The bullet is the same except that because it isn't held by an axle like the tire is, the imbalance will make it wander slightly from its original path. The limitation we face on rate of twist, is that although we want it to be slow for accuracy, we need a certain amount of twist for stability. The 1:11" twist will stabilize all useful match bullets, whereas a 1:12" twist is marginal with some 190 gr. bullets and all of those that are heavier. Accordingly, we can rule out the 1:10" twist as unnecessarily fast, the 1:12" as potentially too slow, and settle on the 1:11" as being just right. Accuracy won't necessarily suffer much with a 1:10", so if you have one, that's fine, if a touch less than optimal. I would avoid the 1:12", however, because it will limit your bullet choices.
Here's something on barrels that also might help.
Length & Contour - Long and heavy is the rule of thumb for a .30-06 barrel. Let's start with length; I consider 28" to be the ideal length for a 30-06 barrel. This is long enough to take full advantage of the powder charge you're burning. Although a 30" barrel will give slightly higher muzzle velocity (about 25 fps) given the heavy contours that are called for, I prefer to keep the length at 28" to reduce fatigue during a string. If you're shooting F-Class or another form of supported shooting, then a 30" barrel can be worth considering, but nothing longer than that for reasons we'll discuss in a Part 2.
There is no reason to use a short (under 28") barrel on a .30-06 when you have the choice; of course, if you're working with an existing barrel that's a different matter, but you won't get quite the performance level of the right-size barrel. When you burn 53 to 60 grains of relatively slow burning powder, you generate a lot of hot gas ready, willing, and able to push the bullet to a high muzzle velocity, you need to give it room to work and that's what happens as the gas pushes the bullet up the length of the barrel. A .30-06 would see increasing muzzle velocity from a barrel as long as 45"; while that's not practical for a host of reasons, don't cheat yourself of a real ballistic advantage by cutting the barrel off too short - they don't grow back.
When picking a barrel contour, weight is your friend. Yes, the .30-06 generates more recoil than a .308, that's just basic physics; shoot the same bullet at a higher MV with more powder and you get more recoil. If you shoot a heavier bullet, as you should, then you get even more recoil. Now, this additional recoil isn't objectionable, even a tired old desk jockey with a bum shoulder (yours truly) can handle it, but a heavy barrel is one of the ways to make it reasonably comfortable. Normally I use the MTU/AMU profile that all the makers offer (Krieger #9), although I have a couple of heavy Palma barrels (Krieger #14) that work out well also - 6.5 lb. of barrel weight is your friend.
These aren't all the answers but I hope they help.
Good luck
Cheer's
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