Twist rates and the math involved

[Mateo]

I need some help. I'm preparing to order my first barrel ever and have some tough decisions to make. I know the contour I want, I'm pretty certain I know who's making it for me (Ron Smith barrels, local guy here in Alberta) and I know what I'm chambering

It will be a 6.5mm tube chambered in 6.5 SS.
My biggest unknown right now is twist rate. I could go 1:8 and call it safe.
But..... The guys at GAP are using 1:8.7 twist on their 6.5 SAUM (very similar cartridge with near identical velocity.) I suspect they are mostly designing theirs to shoot the 130 gr berger VLD's.
I'm hoping my rifle will like the 150gr Matrix VLD's. I do plan on the 130's for deer and punching holes in paper, but for long range and bigger animals in counting on the 150 gr bullets.
How much faster will I need to spin them to use the 150 gr?
The lowest altitude I'll shoot in is 2200 ft. Most shooting will be closer to 4000 ft.
Speed will be 3200 fps with the 130 gr
And. 3000 fps with the 150 gr. ( estimated of course but real world should be real close)
The 150 gr Matrix has a length of 1.430"
barrel will be 26" long
The barrel manufacturer I'm going to visit is able to do gain twist. I like the idea of easing the bullet into a tight twist like 1:8.
Patiently await any help and ideas here. Thanks guys.


What's the

 

[Deleted member 46119]

IIWM go 8. Oh, I did.

I have not tried gain twist yet. I do know that torque moves even the 7kg rifle.

 

[elkaholic]

Hi Mateo...........With the 150's you could get away with 8.5 but I would go with an 8. This is definitely true if you ever want to shoot the 160's, and you might! The 8 twist won't hurt you at any rate. You can go to the berger bullet site and they have an easy calculator for twist rate required. When will you be ready for a reamer?.............Rich

 

[nosualc]

+1 on Bergers spin rate calculator. Better to overspin than underspin.

-nosualc

 

[Mateo]

Thanks for pointing me towards the berger twist calculator! Neat feature.

Rich, it most likely will be spring before I order the reamer
Got the barrel coming soon but still need the action.

 

[elkaholic]

Thanks for pointing me towards the berger twist calculator! Neat feature.

Rich, it most likely will be spring before I order the reamer
Got the barrel coming soon but still need the action.

No seasons open now anyway

 

[Mateo]

No seasons open now anyway

I wish that was true. I have an elk draw for January. Gonna have to use the battered ol' .270 still.

 

[elkaholic]

I wish that was true. I have an elk draw for January. Gonna have to use the battered ol' .270 still.

I forgot that you live up there in Gods country. That battered ol' 270 will probably still make a hole............Rich