What twist and how many lands/grooves for a 6 Creedmoor

[Bigguy1951]

My wife wants to start shooting with me when she can. We both used to shoot competitive archery and bowhunted together. I want to build her a 6 creedmoor as she is not a recoil fan but she can handle a 6mm without any problems. She has harvested a number of deer with a .243. Anyway I have pretty much settled on a 7.5 or 7.7 twist barrel but the number of grooves, from 3-6, stumps me some. Is there an advantage with any of the various groove/lands counts?

 

[Evan]

Why such a fast twist? I'd go 8 twist and shoot everything but the 115s, which aren't much of a loss.

Lands/grooves aren't a big deal and there is no right answer, just get whatever is available off the shelf.

 

[Walt Krafft]

I use 7.5 twist 5R Bartlein's. It shoots any bullet I decide to shoot. But, any number of grooves will work and an 8 twist will do just about anything.

 

[ballisticxlr]

8 twist will shoot 115's but compromises BC a very small amount.

I personally like 3-land, 8twist 6mm bores.

 

[abishai]

I think the bartlien 7.7 5r .237s are purdy special

 

[10XSHOOTER]

Kreiger 5R. Just built one with a 1-7 to shoot the 110 MK

 

[Bigguy1951]

Thanks all for the replies. I will just take the leap and see what works.

 

[Ironworker]

I have a Bartlien 8" twist and it shoots 115 DTAC just fine.

 

[Dgd6mm]

My opinion on the number of grooves a barrel has doesn't make a difference. You did mention twist, go 7.5". Personally I like the .237 bore for heavy 6mm bullets such as the 115 DTAC, tho they are not mentioned in your post.

 

[FrankG]

For the most part accuracy and barrel life wise the style and number of grooves doesn’t make a difference. Some say if you want hardcore accuracy you want conventional style rifling. Basically where the lands meet the groove with a 90 degree corner. I only agree with this in regards to the short jacket 6mm bullets in the 65-70gr range for short range BR guns. That’s because of the short bearing surface of those bullets and it’s worse with a boat tail bullet but once you start getting to the longer/heavier bullets this seems to disappear.

That being said it’s been proven by bullet and ammo makers that the 5R rifling does help fight bullet failure and helps long range accuracy. This was just confirmed to me earlier last year so it’s not just me making the claim on my own. Obermeyer also said years ago that it was better but I never heard what he based that on. How does it help? The odd number of lands and grooves as the bullet makes the jump from the case to the rifling distorts and upsets the bullet jacket less. You don’t get the same benefit per say from a 3 groove barrel even though it’s a odd number groove barrel. Usually the 3 groove barrels the lands are really wide. Like a 50/50 land to groove ratio. So you still have part of one land opposing another land.

We’ve made barrels in 2 groove, 3 groove, 4 groove, 5 groove (conventional), 5R, 6, and 8 groove in standard calibers and again accuracy wise I don’t see a difference. I do believe in the 5R rifling helping fight bullet failure. Again this is more of a problem in the smaller calibers like 6mm.

We’ve also made 7 groove barrels in 50cal and 10 groove barrels in 20mm as well as the 12 groove type barrels for ammunition test barrels as well in given spec calibers.

Other places like AI did a test around 2 years ago for they’re team barrels. They did a test with half of the barrels being 4 groove and half being with 5R style rifling. After the test they went to all 5R rifling and the main caliber they are all running is 6mm.

I just did a another round of quick testing and it’s early in the testing in 6.5CM with a barrel I rebored/rerifled from 22cal to 6.5mm. 5R rifling and 1-8 twist. Shot Hornady 135gr ATIPs from 117 yards to 430 yards and was getting accuracy from .21moa to .32moa. Barrel only has 36 rounds on it as of right now.

Later, Frank
Bartlein Barrels

 

[Bigguy1951]

Thank you Frank for taking the time to give such a great response. I had it down to 3R or 5R but now I will definitely go with the 5R.

 

[FrankG]

Thank you Frank for taking the time to give such a great response. I had it down to 3R or 5R but now I will definitely go with the 5R.

Your welcome! We’ve also made two different 4R style rifling barrels as well. Running one job for one customer right now and they have to be 4R style.

Again no difference in accuracy and if it was my choice....I’d still go 5R.

Later, Frank

 

[FrankG]

That customer that had to have the 4R paid a tooling charge as we had to make a custom tool. Where not doing it as a standard offering.