Help With 6.5 Gibbs

[cutter4ever]

I just purchased a rifle chambered in a 6.5 Gibbs. Model 70 action, custom Douglas 1 and a half inch diameter 30" long Stainless 1 in 9 twist barrel. I've ordered dies so i can fireform some 270 brass. Then I'll send them to Hornady to have a hydraulic case former made. If anyone had any load data/ballistics for the Gibbs, it would be greatly appreciated. This is my first so called wildcat, so any help with anything would be great. Tks

 

[BEEMAN]

Similar to the 6.5 Sherman. Which lots of guys on here are shooting, including myself. Try the search on here for 6.5 Sherman loads. Just be sure to start low and work up. In my Sherman slower powders have worked the best. N570 and R26 with 140 gr to 160 gr bullets. Some guys do use H1000 and Retumbo as well. H1000 was ok in mine but couldn't touch the speed of the N570.

 

[DocDoc]

Twist may limit the weight bullet you can use. Most heavy 6.5 bullets need a 1 in 8.

 

[BEEMAN]

Good catch Doc. I did not see the 1 in 9. That is to bad because it will really limit you on some good heavy bullets.

 

[sable tireur]

That is to bad because it will really limit you on some good heavy bullets.

It's not the weight, it's the length of the bullet that calls twist rate into play. And besides, how heavy do you think you need to go and what bullets does this eliminate?

I'm shooting the Hornady 143 ELDX at 3100 fps and it stabilizes in a 1:9" twist. So does the 140 grain Berger.

The only one that is on the edge is the 160 Matrix.

Name the others that you have determined by shooting to be unstable in the 1:9" twist using the Gibbs cartridge.

Regards.

 

[BEEMAN]

As I said I shoot a Sherman so no experience with a GIBBS. But according to both Berger and Matrix they all recommend a 1 in 8 twist. Even the Berger 130 gr recommends a 1 in 8. As far as how heavy to shoot; is that not the reason for the Gibbs and the Sherman to be able to push heavier bullets faster? I have shot Matrix and Berger but I have a 1 in 8 and all bullets have been stable. The 1 in 9 may work if you are at a certain altitude etc. But if I was to build one I would still choose a 1 in 8 twist. Good to hear about the 143 ELD-X. Wish I could find some in Canada.

 

[sable tireur]

Matrix and Berger, Sierra, Hornady, Speer, Nosler and any others I didn't list will ALL pick the smallest capacity cartridges for a bullet weight class and then recommend the twist rate. In this way they insure that the bullet will be stable no matter which cartridge the public chooses to load with their bullet. This has been a practice for a couple of decades at least.

That's why I was asking if you had any experience with the bullets and the 1:9" twist rate. The 1:9" will stabilize all but the 160 Matrix at the velocities attainable for the 6.5 Gibbs. The same can be said for many of the longer VLD bullets in specific calibers such as the 75 and 80 grain AMAX bullets in .22 caliber will be stable when fired in a 1:10" twist rate when the cartridge produces enough velocity. I've accomplished the same thing with these in a wildcat 22-243 AI as I have with the above 6.5 bullets in the Gibbs.

However, if I was to fire the 75 and 80 grain AMAX in a .223 Rem. cartridge the twist rate would necessarily need to be faster due to the significantly lower velocity.

The bullet manufacturer's suggested twist rate is a guarantee that the bullet will be stable at the lower velocities.

Regards.