Twist rates for 6br

[leadfarmer]

I have a kauger action that needs a barrel and I'd like to do a slow twist 6br for club matches, shooting out to 200 yard bench and 300 yard fclass. I'd be strictly using 68gr bullets.

I was planning on going with a 13.5 twist, but this club shoots all throughout the winter months where it can drop into the 20s and 30s. Would the 13.5 still stabilize the 68gr. Every calculator I type this into says it's marginal, which has me hesitating and maybe thinking a 13 or even a 12 twist.

 

[sbindy]

I wouldn't have a problem with a 12 twist.

 

[Trigger-Jerker]

In a 6br I doubt you’d notice much difference between 13 or 13.5 twist with 68gr projectiles.
If you decide on a 12 twist that opens the option to shoot 80gr bullets.

 

[Steve Kostanich]

Just put a 14" twist on my 6 BR short range rig. In initial testing, just guessing at a starting load, I fired a 5 group agg @ 100 yds of
.2044. Felt pretty good about it. Load was 30 gr. of 3032, my 65 gr. bullets and Br-4 primers, Lapua cases.
Yes RG that 3032 stuff is OK!!!

A 13.5 or 14 twist barrel should be OK for you.

FWIW
Steve Kostanich

 

[R.G. Robinett]

For the classic 68 Gr. FB bullets, based upon the .825" long jacket (finished FB length about 0.85"), you'll be money ahead opting for a 1:13", or faster: MUCH better HUMMER:bummer ratio. Think length, not weight, that latter of which is just, "along for the ride".. Put a BT on the bullet and go straight to 1:12" and never look back - with. either FB, or, BT, you'll get a LOT fewer head-scratchers . . . and the shorter/lighter bullets will still shoot GREAT. RG

P.S. Steve, I'm betting that your 65 Gr. are based upon a .790", or shorter jacket, for which a 14" twist is cat's meow.
Mr. Mike Walker advised us (PRECISION SHOOTING letter to editor), WAY back when j4 decided to make the .825" jacket, " not to make a 68 Gr. bullet using that jacket length and expect it to be compatible with the 1:14" twist barrels! But everyone looked around and said . . . "but, it's a 68 Gr. bullet", and continued to test the physics for 40 years or so. In short, the 1/32nd inch length difference is worth a full inch of twist rate requirement: Mr. Walker wasn't exactly the village idiot.

 

[todde]

Hummer - bummer ratio. That made me laugh.

 

[Steve Kostanich]

RG,
Yes the bullets I fired the .204" agg with were 3 groups with a .790" jacketed bullet and 2 groups with a .750" jacket.
Sure wish Berger still supplied the .750" jackets! I have one bucket left.

Steve Kostanich

 

[Hunter]

For the classic 68 Gr. FB bullets, based upon the .825" long jacket (finished FB length about 0.85"), you'll be money ahead opting for a 1:13", or faster: MUCH better HUMMER:bummer ratio. . . .

Mr. Mike Walker advised us (PRECISION SHOOTING letter to editor), WAY back when j4 decided to make the .825" jacket, " not to make a 68 Gr. bullet using that jacket length and expect it to be compatible with the 1:14" twist barrels! But everyone looked around and said . . . "but, it's a 68 Gr. bullet", and continued to test the physics for 40 years or so. In short, the 1/32nd inch length difference is worth a full inch of twist rate requirement: Mr. Walker wasn't exactly the village idiot.

No wonder some of my 6PPC groups stink; 14 twist barrel, and 68 gr FB bullets with a finished length of about 0.84". All this time I've thought the shooter was the problem.

 

[R.G. Robinett]

No wonder some of my 6PPC groups stink; 14 twist barrel, and 68 gr FB bullets with a finished length of about 0.84". All this time I've thought the shooter was the problem.

The 1:14 isn't a wreck - just not quite rock-solid - one of the gremlins that is always there to disrupt. RG

 

[treece]

6br 12twist with 80grainers is hard to beat.
Varget,4895, RL15.5 for powder