22 CM barrel twist

[deerhunter628]

I am considering getting a 22 CM barrel made for one of my rifles. I am leaning towards a 19” barrel. I have the following twist options: 1:6, 1:6.5, 1:7, 1:8. Is there a disadvantage to the 1:6? Which twist would you choose and why?

 

[mighteywhitehunter]

Just got my CBI barrel from NSS. I went 20" in their lightest sporter contour in 1-7" twist saami chamber. So far it has shot very well with Hornady 80 ELDX factory ammo. First 20 shots of factory ammo averaged 3110 fps and were .5-.75 moa.
My plan was to shoot the Barnes LRX 77gn and various lead bullets in the 77-88gn range at decent speeds, thats why I went with a 20in bbl and 1/7 twist.
I dont think you need anything faster than 1-6.5" to shoot any bullet currently made.
The potential disadvantage would be if you are really trying to push the velocity envelope with the extra fast twist you may start blowing up bullets unless you are shooting copper monos.

 

[deerhunter628]

Just got my CBI barrel from NSS. I went 20" in their lightest sporter contour in 1-7" twist saami chamber. So far it has shot very well with Hornady 80 ELDX factory ammo. First 20 shots of factory ammo averaged 3110 fps and were .5-.75 moa.
My plan was to shoot the Barnes LRX 77gn and various lead bullets in the 77-88gn range at decent speeds, thats why I went with a 20in bbl and 1/7 twist.
I dont think you need anything faster than 1-6.5" to shoot any bullet currently made.
The potential disadvantage would be if you are really trying to push the velocity envelope with the extra fast twist you may start blowing up bullets unless you are shooting copper monos.

Good call. I do not plan to use monos.

 

[khuber84]

I'd say 7 or 7.5 to do all things well. If you want to run the heaviest mono metal bullets the 6 may be necessary but it probably will blow up the others due to over Rev at higher velocity.

Make sure it's 219 bore diameter, not 218.

 

[43.6N]

What bullet are you going to be shooting?
What altitude?
How long of a barrel?

14.5-16” I’d go with 1/7”
18” would be perfect at 1/7.5 (but not a listed option)
20” or longer I’d go with 1/8.

The math depends on calculating bullet rpm at your target velocity. Too fast and they’ll explode in the air. Too slow and they won’t be stable in flight.

 

[deerhunter628]

What bullet are you going to be shooting?
What altitude?
How long of a barrel?

14.5-16” I’d go with 1/7”
18” would be perfect at 1/7.5 (but not a listed option)
20” or longer I’d go with 1/8.

The math depends on calculating bullet rpm at your target velocity. Too fast and they’ll explode in the air. Too slow and they won’t be stable in flight.

Im planning 19” and want to shoot heavy lead core bullets. My altitude is about 1000 ft. They do not list 1:7.5 as an option. Im thinking the 1:7.

 

[43.6N]

Im planning 19” and want to shoot heavy lead core bullets. My altitude is about 1000 ft. They do not list 1:7.5 as an option. Im thinking the 1:7.

Sounds reasonable.
If you do find bullets popping in the future, before you scrap the barrel try dropping your charge by 1-1.5gr and seeing if the lower pressure and velocity fixes the problem.

But from a stability standpoint, absolutely no reason to buy a faster twist rate in my opinion.

 

[khuber84]

My latest is a 7 twist 6 groove 219 bore Ace, 150 freebore finished at 18". Running N555 and 88 eldm at 3040ish. Shoots pretty dang good. I think the 6 groove 219 bore will help reduce jacket stress as fire cracking starts to happen. Hopefully preventing bullet failure. Once I start to see a problem I'll likely switch to a 77tmk as I have pushed them very hard in a 7.5tw 3500mv, and no problems.