Twist Rate in SBR. Will 1:9 Do?

[zekers7]

Thinking of picking up one of the J&T discount barrels and having it chopped down to 12.5"

will the 1:9 twist do a good job of stabilizing mostly 100gr wolf ammo? I have an 18" match barrel that I use for hand loaded 123gr.

[rabiddawg]

Iirc, Bill Alexander recommends a faster twist with short barrels. Like 1/7.5

Search it. It's on here somewhere

[sneaky one]

Also depends on bullet wts. It's trial and error--- or pm Cory.

[danm]

I'm planning a 12.5" pistol build and I'm going 1:8... My 18" BHW is 1:9 and works with everything I've shot, not sure how well 1:9 will work for SBR lengths.

[BluntForceTrauma]

First, twist rate will depend on your velocity and bullet length. The best tool is always Berger's Twist Rate Calculator. Follow the instructions and enter in your data and you will have your answer.

In general, the shorter the barrel and the lower the velocity and the longer the bullet — whew! — the tighter twist you'll need.

In general, a tighter twist helps accuracy at long range and has hardly any effect on velocity, so there's almost nothing to lose going tighter. A win-win.

Guys will argue that there IS such a thing as too tight, and that there is an optimum twist for a given bullet/barrel combo, and I guess I feel no need to strongly disagree, but I haven't looked deeply into that issue. Like so many things, even the experts disagree, so THEN what do you do?

Anyway, Bill A. is always very thorough in his approach, and planned his twist rate for the lowest common denominator — for example, some guy shooting 140-grainers from an SBR in cold weather at sea level. So, if you're not shooting worst-case scenarios, you might not NEED as tight a twist as he uses. Again, your answers are in Berger's calculator.

[VASCAR2]

I have the J&T 16" chrome moly 1:9 twist 6.5 Grendel. Mine stabalized the Wolf 100 grain FMJ fine out to 200 yards. This is the furthest I've shot the steel case ammo. The Wolf runs from about 1.5-3 MOA in my J&T and just isn't super consistent. Honestly a 9" group at 300 yards is still definitely minute of man accurate but factory 123 grain A-Max will shoot 3" groups at 300 yards. The 123 grain bullets have been stable out to 800 yards in my 16" 1:9 twist.

If I were betting I'd say a 12.5" 1:9 twist 6.5 Grendel will even stabalize the 123 grain bullets. Maybe someone else will chime in.

[cory]

I imagine that you'd be fine with the 100gr stuff. However, I wouldn't be surprised if the wolf was to low of pressure and the 123gr was to heavy. Nor would I be surprised if it shot these great. You're heading into uncharted territory brother, where you will be right on the edge.

I think you'd be better off getting one of the faxon barrels in the GB and chopping it down. Or I think there's a SBR Faxon Barrel GB going on over at ARFcom.

[zekers7]

I have the J&T 16" chrome moly 1:9 twist 6.5 Grendel. Mine stabalized the Wolf 100 grain FMJ fine out to 200 yards. This is the furthest I've shot the steel case ammo. The Wolf runs from about 1.5-3 MOA in my J&T and just isn't super consistent. Honestly a 9" group at 300 yards is still definitely minute of man accurate but factory 123 grain A-Max will shoot 3" groups at 300 yards. The 123 grain bullets have been stable out to 800 yards in my 16" 1:9 twist.

If I were betting I'd say a 12.5" 1:9 twist 6.5 Grendel will even stabalize the 123 grain bullets. Maybe someone else will chime in.

Is the faxon GB running through the forum here?

[cory]

Yes there's one running in both.