280 AI Rate of Twist and Contour

[#publiclands]

What is the recommended rate of twist for a 280 AI? Plan to shoot 130-160+ grain bullets. Any suggestions or recommendations would be appreciated.

 

[tam9492]

Interested in this too. I’m seeing 8.5. I know there’s also some info on minimum barrel length to really see the benefits from the cartridge. Will 24” get it done?

 

[passinggas33]

I’ve got 2 280AIs. One is the Kimber Mtn Ascent. It has a 24” barrel with a 1-9” twist if I’m not mistaken. The other is a custom that is also a 24” barrel with a 1-8” twist. I’m pretty happy with the length though I feel you could probably go as short as 22” and still have the vast majority of the benefits of this gun. As for the twist, I can get 160 grain bullets to stabilize in the 1-9” at the current length. Not sure I could if I shortened it anymore?? As for the 1-8” twist I can get 180 grain bullets to stabilize. Not sure if that helps you or not, but wanted to share what I have found. IF I were to do it all again, I would do a 1-8” twist in a 22” barrel (because I shoot suppressed). Then try and see if I could get something in the 170 range to be accurate and stable. That TO ME would be the perfect combination.

 

[Bater]

Depends on what 160gr bullets you want to shoot. Big difference in twist requirements for say a 160 AB compared to a 162Eld-x/m. My 24" 9T stabilizes a 162 Eld-x past 1k just fine

 

[MuleyFever]

My new one that is coming will have a 8.5 twist. My Montana has a 9 twist and loves the 160AB.

I would not go shorter than 24" personally. If you wanted a shorter barreled 7mm I would just go with the 7mm-08. Build it on a Tikka or medium action and you can easily shoot 160's. Or a short barreled 7 SAUM.

 

[CApighunter]

I did an 8.5 on mine. If going custom I’d do 8-8.5, while not need for those bullets it gives you more options down the road.

 

[tam9492]

So if going 24”, 8.5 should suffice. Could potentially go 22” at 8?

 

[Bater]

You can go as short as you want, won't affect bullet stabilization if that's what you're asking

 

[SteveCNJ]

My Weatherby backcountry has a 24" 1-9 twist. I will be working on loads with a few different options but it's been pretty good with factory 160 Nosler Accutips.

Sent from my SM-G996U using Tapatalk

 

[Harvey_NW]

I'm shooting 162gr ELD-M out of a 24" 1:9 holding sub MOA out to 1k.

 

[rootacres]

Id go 8.5. My Proof (7 SAUM but basically the same thing) is an 8.4. It shoots the light monos really well all the way up to the heavies. I don't really think you can over stabilize a light bullet but you can under stabilize a heavy one.

 

[#publiclands]

So what I’m reading is the longer the barrel the higher twist you should get. 22” -8, 24”- 8.5, and 26” - 9? Seems like 8.5 is the recommended and most used for the 160 and heavier but 9 will work?

What about for the 130-160, will the 8.5 and 9 stabilize then well?

Does the barrel contour change things? Does a heavier contour (#4 or 5) help with the bullet stabilization and accuracy?

 

[eoperator]

24" 1:8 for the win

 

[#publiclands]

The guys over at Shaw Barrels recommend a 9.5. What does everyone else think?

 

[Harvey_NW]

So what I’m reading is the longer the barrel the higher twist you should get. 22” -8, 24”- 8.5, and 26” - 9? Seems like 8.5 is the recommended and most used for the 160 and heavier but 9 will work?

Not exactly. Faster twist is required for the longer the bullet is for it's diameter. Barrel length has no direct effect on stability, but it does on velocity, which affects RPM, so it technically does. Those differences in length are negligible unless you were riding the knife edge of stability. Easiest way to quickly determine what you need is to use Bergers or other stabilization calculators to confirm what you want to shoot will stabilize at the elevations you plan on shooting or hunting at.

What about for the 130-160, will the 8.5 and 9 stabilize then well?

Yes, 8.5 should stabilize both. I'm shooting 162gr ELD-M through a 24" 1:9 with no issue. I've shot 168's through a 1:9.5 with no issue as well.

Does the barrel contour change things? Does a heavier contour (#4 or 5) help with the bullet stabilization and accuracy?

No/possibly. Twist rate and velocity determine stabilization. Heavier contours can withstand vibration and heat better, but in terms of accuracy doing load development with a sporter barrel will mitigate that because you can tune harmonics with powder charge.

The guys over at Shaw Barrels recommend a 9.5. What does everyone else think?

If you plan on shooting 160+, I would not recommend a 9.5. Going with a 1:8.5 and over spinning a 130 likely won't have a negative affect on accuracy, but under spinning a 160 will. Again, plug some numbers into a calculator.

 

[Harvey_NW]

Bullet RPM = MV X 720/Twist Rate (in inches)

 

[KoolBreeze]

Very limited, short range only, experience here but my xbolt is 1:8 with a 24" barrel. It doesn't like the 140 accubonds much but loves the 155 terminal ascents and 160 accubonds.

 

[#publiclands]

So would an 8.5 be the twist you would recommend as a good all around twist that would shoot the lighter to the heavier bullets. Not set on a particular bullet brand, type or weight. Just need to know before I buy my barrel or rifle. I understand that is all varies once you get into the specifics but just trying to narrow it down. Thanks

 

[Bater]

Yes, 8.5 would work for about everything

 

[Max Draft]

I just got in a CA Ridgeline in 280AI and it's got a 26" barrel with a 1:9 twist. I think I would have preferred a 24" barrel over 26. When I was researching them I feel like I usually found a 1:8.5 most common.