.270 win Rebarrel twist rate questions

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BJEoutdoors

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I am thinking about a rebarrel for my .270 win. Possibly a Shilen. To get down to the meat of the question, if I rebarrel in a 1-9 twist to handle some of the bigger bullets better, such as the 165 matrix and the 180 Woodleigh, what are the lightest bullets it should still shoot effectively? I would still like to shoot the 130's and possibly the Barnes 110 ttsx, just with the ability to shoot the Matrix for longer range and the Woodleigh for bigger game. Thanks, Ben
 
Ok, thanks. That's what I was hoping. Now I just need to make up my mind on whether I want to keep it .270 or go .30-06 haha. Such a hard thing to do when you like both! Also, I appreciate your service to our country.
 
The TTSX is very long for it's weight and length is really the determining factor for twist rate. People really only talk about "weight" because typically heavier and longer go together. It's only when you take out the lead and make a monolithic copper bullet that you run into incongruities.

In any case, there are a number of stability calculators that can give you an idea of the ideal twist (or compromise) for the weight/length range you intent to shoot. I like JBM but there are others. JBM also has a bullet length database for that (necessary) info.

Here's some others:
http://www.bergerbullets.com/twist-rate-calculator/
http://www.geoffrey-kolbe.com/barrel_twist.htm
 
When you get to the calculators, using the Kolbe one based on the late Robert L. McCoy's program, McGyro, is the most complicated to use, but takes the most factors into account. One thing I don't like about it is the density selection often isn't very close to correct. But not to worry. Kolbe also has a bullet drag calculator. If you enter your bullet in the drag calculator first, you can plug the weight of the bullet in and it will calculate density from the dimensions you give. Then go back to the barrel twist estimator and enter that density into its arguments as a custom number for more accurate results.

Note Sierra's general purpose advice is to have a stability factor between 1.3 and 3.0 for "hunting accuracy" and between 1.4 and 1.7 for optimal match accuracy.
 
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