Does barrel length factor into twist rate?

[vereceleritas]

I've read a lot about bullet length and weight and how those factors contribute to choosing a particular twist rate. When it comes to .308 I can't help but notice that shorter barrels (16-20 inches) are almost unanimously 1/10 twist, especially in gas guns. Meanwhile, barrels longer than 22 inches will tend towards 1/11 and 1/12 twists. Does the length of the barrel matter at all when choosing the proper twist rate? Does it have anything to do with reduced velocities from a shorter barrel or am I just completely off base with my observations?

 

[BobinNC]

Re: Does barrel length factor into twist rate?

If you use the Miller Stability formula, found on JBM, here:

Stability Calculator

You will see that barrel length is not among the inputs. However, velocity is. I think that should answer your question.

Bob

 

[remau308]

Re: Does barrel length factor into twist rate?

Basically, the longer the barrel, the more velocity you achieve. The shorter barrels use a faster twist rate to stabilize the bullets better, but other than that, the length does not factor into twist rate. If this is a decision for what barrel you want on your rifle, you will be happy with a 20" 1:10, or a 26" 1:11/1:12. The shorter the barrel, you will want a faster twist rate, and it will perform flawlessly...most of the time. I have seen a 20" get out to 1000yards easily.

 

[map_it]

Re: Does barrel length factor into twist rate?

I ordered a barrel with a finished length of 22" and they recommend me go with a 11.25 rate. I plan to cut it off at 20" because I have since fell in love with suppressors...I do not think it will matter 20" or 22". If you hand load I was told the 20" will perform as well as any 24" or 26" at range.....

 

[eleaf]

Re: Does barrel length factor into twist rate?

If it matters any, GAP is recommending a 1:11.25" twist for all of their .308 rifles regardless of length. At least they did when I ordered mine about a month ago.

I settled on a 20" Varmint contour with a 1:11.25" twist. It should push anything up to 180 grainers with no issue.