Need some rifle twist experts to help me out...

[MudRunner2005]

Need some rifle twist expertise....

I know that just like with bullet diameter vs case volume, velocity vs twist rate can also reach a point of diminishing returns. This is hypothetical, but I am hoping we can have a good solid debate and I can get some solid answers.

If you were pushing a Berger .224 90gr VLD down a 26" barrel, at between 3,800-4,200 fps, would you need a 1:7 twist, 1:8 twist, 1:9 twist, 1:12 twist, or 1:14 twist?

I am thinking 1:12 twist, simply because barrel length and bullet velocity would be traveling SO incredibly fast that the really slow twist rates (1:7-1:9) would hinder it, or cause the bullets to come apart in mid-flight, or as soon as it exits the muzzle... And that the 12" twist rate would stablize the long skinny bullet just fine because of the incredible velocity it would be traveling down the barrel at...

Any help and input would be great. Thanks!

 

[Sully2]

Ya cant arrive at the right answer without knowing what RPM the bullet was designed for!??? If designed for 90,000 RPM and any of those twists make it twirl at say 120,000.....the bullet will blow apart with any of them

 

[Edd]

A 12" twist won't stabilize a 90 gr Berger at any velocity. Velocity does very little to substitute for twist. A 90 gr Berger is less stable with a 7.5" at 4000 fps than it is with a 7" twist at 3000 fps.

If you are going to shoot a 90 gr Berger, you need a 7" twist or faster.

 

[MudRunner2005]

I'll shoot Ryan Neal an email and ask him...

Thanks for that info Sully.

 

[MudRunner2005]

A 12" twist won't stabilize a 90 gr Berger at any velocity. Velocity does very little to substitute for twist. A 90 gr Berger is less stable with a 7.5" at 4000 fps than it is with a 7" twist at 3000 fps.

If you are going to shoot a 90 gr Berger, you need a 7" twist or faster.

All I can find are 8 twist barrels... I found a Bartlein 7.7 twist availabe, and a Brux 7 twist, but it's out of stock...

So, a 5R rifled 7.7 twist Bartlein 26" Rem Varmint contour is about my only option available right now.

Would that barrel stablize a 90 VLD at 4,000-4,200 fps?

 

[HARPERC]

I've got no idea what will work, but I've heard a few disappointing stories from credible people, regarding the difficulty of driving heavy .224 bullets very fast.

I am interested in the subject so I'll tag along.

 

[Edd]

So, a 5R rifled 7.7 twist Bartlein 26" Rem Varmint contour is about my only option available right now.

Would that barrel stablize a 90 VLD at 4,000-4,200 fps?

According to Berger, it would be less than ideal but above the minimum requirement.

 

[Mikecr]

So, a 5R rifled 7.7 twist Bartlein 26" Rem Varmint contour is about my only option available right now.
Would that barrel stablize a 90 VLD at 4,000-4,200 fps?

It would blow up a little over 3300fps at that twist.
If not for this, it would still be only marginally stable under ICAO conditions.

It's because of a sharp balance in twist to failure, that the 90VLD is less useful than lighter bullets.

 

[MontanaRifleman]

What overbore barrel burning cartridge are you going to drive 90 gr .224 bullets to 4000 fps and what powder are you going to use?

 

[varmintH8R]

What overbore barrel burning cartridge are you going to drive 90 gr .224 bullets to 4000 fps and what powder are you going to use?

I am curious as well, and am tagging along. 223-EDGE?

Awesome, I want to hear more about it (and if it works!)gun)

 

[MudRunner2005]

It's a project of mine called the .22 Evidentem...And it will be 7828 SSC powder.

I haven't had the reamer or dies made yet, but I will hopefully soon...

 

[MudRunner2005]

It would blow up a little over 3300fps at that twist.
If not for this, it would still be only marginally stable under ICAO conditions.

It's because of a sharp balance in twist to failure, that the 90VLD is less useful than lighter bullets.

That's what I was thinking...Ultra tight twist and alot of speed = kaboom!

So, would a 12" twist work better on that bullet as fast as it will be traveling?

 

[Mikecr]

No, you have misunderstandings of stability.
It's not purely about RPMs. It's about displacement as an overturning force -that revolutions of a bullet resist (gyroscopically).
For that bullet you need 1 turn per 7" of displacement, regardless of velocity.

 

[MudRunner2005]

No, you have misunderstandings of stability.
It's not purely about RPMs. It's about displacement as an overturning force -that revolutions of a bullet resist (gyroscopically).
For that bullet you need 1 turn per 7" of displacement, regardless of velocity.

Gotcha! Ok, that makes more sense now. Thanks for the info.

So regardless of velocity, I will need a 7 twist for that bullet. Period.

However, that bullet at that velocity might explode as it leaves the muzzle because it can't handle spinning at that many RPM's...

Correct?