Hornady 338 ARC

[Oso]

I saw some early videos of 8.6BO in which they experienced catastrophic failure of cup core bullets in 1:3 twist barrel… damaged some suppressors. As I recall, SubX didn’t reliably stay together exiting barrel. Rotational force tore it apart.

Hence my interest in whether or not it survives a 1:5 twist and then how does it perform on target afterward.

 

[SKWERLZ]

I'm very interested in a 1:3 ARC. I have a barrel blank... a reamer.... I wonder if the 307subx would hold together.

I wouldn’t trust it especially if suppressed.

 

[FrankG]

I saw some early videos of 8.6BO in which they experienced catastrophic failure of cup core bullets in 1:3 twist barrel… damaged some suppressors. As I recall, SubX didn’t reliably stay together exiting barrel. Rotational force tore it apart.

Hence my interest in whether or not it survives a 1:5 twist and then how does it perform on target afterward.

The twist is a good one but I've seen barrels made in these really fast twist and there is damage to the lands from the barrels being made during rifling. I've seen pic's posted on forums as well we had a local guy bring in his AR15 in 8.6BO and I won't name the gun or barrel maker but you could see the damage to the lands with the naked eye let alone using a bore scope. The sides of the lands where all chewed up/torn from the button during rifling.

Damage to the lands is going to beat the bullet up more/damage them. Then factor in a really fast twist... nothing but a recipe for bullet failure.

For easy numbers... at 1500fps a 3 twist barrel is going to be spinning the bullet at 360k rpm.

At 1100fps a 3 twist barrel is going to spin the bullet at 264k rpm.

As you approach 300k and exceed it... plan on bullet failure to happen. It will get amplified as the barrel wears and the throat gets rougher... it's going to beat the bullet up more. If the rifling has any damage to it.... you just made the issue worse.

You want to play with really fast twist stuff like this... I feel your more inline with using a solid bullet. Just also keep in mind a really fast twist and if your bullet or loaded ammo has any significant amount of runout... premature wobble if you will.... the really fast twist is going to amplify it and you could see a negative from the accuracy side of things.

Later, Frank
Bartlein Barrels

 

[FrankG]

I have yet to see any data that says... you have to have a really fast twist. Even 300gr 338 bullets will stabilize at 1100fps out of a 7 twist barrel.

I asked a couple of bullet/ammo makers about this as well. Was told the same thing... no need for the 3 twist or even possibly the 5 twist barrels. My opinion and again it's my opinion... the faster spin on the bullet does nothing extra on terminal impact performance. I feel design of the bullet and shot placement is more important here vs the spin rate.

Not starting an argument on the above paragraph.

If someone has really good data to show otherwise... I'd love to see it in order to learn from it.

 

[dantiff2]

The idea and concept of a 1:3 or even a 1:5 twist is great WHEN velo is limited to subsonic velocities. 1050-1065 fps keep your revs under 260,000 rpms.

 

[LVLAaron]

The Q nerds will fight endlessly with you on the twist rate. At the same time they've never tested those bullets out of a 1:5 / 1:8

 

[Oso]

FrankG - Thank you for insight! Buying a budget / generic barrel is a gamble on construction and quality. You and a couple of your barrel buddies have spoiled me on premium barrels. I wouldn’t consider building a 1:3 anything until Bartlein offers the barrel and blesses it For subsonic I’m more interested in 1:5 or 1:6.

As fun as the videos of gel blocks and exploding things are with 1:3 twist, I would have to become a watermelon farmer just to have a consistent source of targets to blow up.

 

[FrankG]

FrankG - Thank you for insight! Buying a budget / generic barrel is a gamble on construction and quality. You and a couple of your barrel buddies have spoiled me on premium barrels. I wouldn’t consider building a 1:3 anything until Bartlein offers the barrel and blesses it For subsonic I’m more interested in 1:5 or 1:6.

As fun as the videos of gel blocks and exploding things are with 1:3 twist, I would have to become a watermelon farmer just to have a consistent source of targets to blow up.

Thanks!

We've done 3 twist and 5 twist barrels. Cost extra money of course. We've done them in 5R rifling and Saami spec 6 groove. The 6 groove barrels where for a ammo maker and a gun maker for testing purposes.

The fastest twist rates we did was for testing for a manufacturer. Sorry have to leave the name out. They buy quite a bit from us.

In 30cal we've done 1-3, 1-2.5, 1-2, 1-1.5 and they asked us for a 1-1 twist barrel. Yes they paid the tooling charges and barrel costs etc... and it wasn't a cheap date. All turned out great except for the 1-1 twist barrel. We had to put so much clearance on the fast side of the tool that it cut away half the land width. Other than that the barrel turned out beautiful. I was going to scrap the barrel and told the maker what happen and wasn't going to charge them for the barrel. The guy in charge of the R&D asked if he could still have it. We sent it to him n/c.

 

[FrankG]

Those really fast twist 1-2 and 1-1 twist barrels etc... look like a internally threaded bolt! Messes with your eyes! LOL!