Optimum 7mm-08 twist rate

[BD1965]

I am about to rebarrel a Seekins 308 to 7mm-08 in bartlein or proof CF. Will be reloading Hornady eldx 150-162 bullets mainly for hunting but also reloading for optimum accuracy out to 800. Prefer 22"but willing to go up to 24". Question: most research says 1:9 twist for this setup, plenty of 1:9 24" around but found a bartlein 22" in stock but it's 1:8.5 twist. Can you go too fast, am I splitting hairs? Thanks for your opinions and merry Christmas!

 

[59FLH]

IMO it's better to be 1 twist to fast then 1/2 twist to slow.

Go 24" or Ackley @ 26"

 

[FrogFire7]

Agreed. Faster is ALWAYS better in my opinion. Unless you are shooting super fast cartridges (or super light bullets very fast) you shouldn't have any concerns about spinning bullets apart.

Its been a while since I've read about it (haven't ran into the issue myself) but there are some general guidelines about how many RPM's you have to be concerned about with spinning bullets apart mid flight. There are also some easy calculators for figuring out your RPM's if you don't want to do the math yourself.

The other big advantage to fast twist (in my opinion) is that should you choose to shoot copper mono bullets you won't be as limited to the lighter bullets (if you are thinking about trying to shoot heavier ones for higher BC).

 

[Hard rock]

IMO it's better to be 1 twist to fast then 1/2 twist to slow.

Go 24" or Ackley @ 26"

I would prefer the 1-8.5 over the 1-9 , it gives you more versatility , especially with mono bullets . You won't be disappointed . Copper is not as dense as lead , so a 140 mono is as long as a 160 cup and core and you can't over spin them . 1-8 twist would even be better.

 

[Beluebow]

A 9t is plenty for the bullets listed.

 

[Wachsmann]

I would do a 1/9 minimum. Look at a stability calculator so you can figure out what you need. I run the 168's in mine but they are not fully stabilized per the calculator so I think I loose a little BC from that. It always good to have a little more than not enough.

 

[Another Casual]

Minimum of 1:9 if you're sure you will stick to 160 and below. On barrel length, I have a thread where I cut my 7mm08 down from 26" to 20" and was happy with the results. Might help you decide on what length to go with. A bartlein #3 is about .720" at 20" and can be threaded 5/8, if that helps. Southern precision has them in stock currently.

 

[Justice1327]

I have experimented with 708 and bullet weights that you mentioned. I have a 7 mm 08 AI with an 8 twist and a 9 twist as well as a 7-08 in the 9twist and an 8.5 twist. i've always found much better results with a one and nine twist, even shooting the 162/168 gr. Better velocity not so much stress on the bullet. When I built my 284 Sheehan, I went with a one and nine twist, and I shoot the 180 Bergers just fine. But I did have to go to the 8.5 to shoot the 184s properly. The velocity increase helps stabilize the bullet in the 284. All of my 280s, 7 mm Rem mags, 7 SS and my new 7mega all have 9 twist and shoot 162-175 great. my 7PRC that is being built will have an 8 twist because I plan to try 184-195.

 

[BD1965]

Thanks very much for the specific details of your experience sir

 

[BD1965]

I would do a 1/9 minimum. Look at a stability calculator so you can figure out what you need. I run the 168's in mine but they are not fully stabilized per the calculator so I think I loose a little BC from that. It always good to have a little more than not enough.

Thanks very helpful, what twist do u shoot?

 

[BD1965]

Minimum of 1:9 if you're sure you will stick to 160 and below. On barrel length, I have a thread where I cut my 7mm08 down from 26" to 20" and was happy with the results. Might help you decide on what length to go with. A bartlein #3 is about .720" at 20" and can be threaded 5/8, if that helps. Southern precision has them in stock currently.

Thanks good to know I live <3 hrs from southern precision and definitely will read your thread too!

 

[BD1965]

I have experimented with 708 and bullet weights that you mentioned. I have a 7 mm 08 AI with an 8 twist and a 9 twist as well as a 7-08 in the 9twist and an 8.5 twist. i've always found much better results with a one and nine twist, even shooting the 162/168 gr. Better velocity not so much stress on the bullet. When I built my 284 Sheehan, I went with a one and nine twist, and I shoot the 180 Bergers just fine. But I did have to go to the 8.5 to shoot the 184s properly. The velocity increase helps stabilize the bullet in the 284. All of my 280s, 7 mm Rem mags, 7 SS and my new 7mega all have 9 twist and shoot 162-175 great. my 7PRC that is being built will have an 8 twist because I plan to try 184-195.

I really appreciate the specific details of your experience thank u sir

 

[BD1965]

I would do a 1/9 minimum. Look at a stability calculator so you can figure out what you need. I run the 168's in mine but they are not fully stabilized per the calculator so I think I loose a little BC from that. It always good to have a little more than not enough.

Found Berger's calculator on their site thanks

 

[Elkeater]

My 7-08ai version is 24" with an 8 twist proof. I shoot 120 vmax, 140 absolute hammers, and 168 Berger VLDs all into sub .5 MOA.

I'm not convinced you can really over twist a bullet unless you start getting really fast and start spinning bullets apart.