6.5mm Barrel Twist

[fclasser20]

I am looking at building a 6.5 and I was wondering if an 8.5 twist can stabilize the 140 class bullets, or do you need to go to an 8 twist?

 

[jedi8541]

When I built my 6.5X47L I started with a Krieger 1:8.5. I was told that it was fine. But with this new Broughton I have it is a 1:8 and shoots lights out. I shoot the Sierra 142 grain.

 

[bugsplat]

Yes. I shoot a 8.5 in my 6.5-284 with 140gr VLD's and they give me 1/4moa groups. I don't hot-rod much though and keep it around 2900fps.

 

[HillbillySniper]

The last I knew there wasn't an up charge for a different twist why not just play it safe and git the 8 twist you can't really over stabilize your slug.

Hillbilly

 

[bowslngr]

If you run the numbers in a stability calculator, an 8.5 twist is just about ideal for all the 140s.

 

[dennisinaz]

The last I knew there wasn't an up charge for a different twist why not just play it safe and git the 8 twist you can't really over stabilize your slug.

Hillbilly

I think you can. You don't want to spin a bullet any faster than you have to. Look at what twist the short range 30 cals are- they are using up to 18 twist barrels now. How do you think that 10 twist whisper is going to do with a 110 grain BR bullet??


I run 8.5 and 9 twists in 6.5mm. The 9 seems to do about everything short of the 140VLD and 142 Sierra. It will stabilize the 130s in my rifles. The 8.5 works with 140 Bergers and 142 SMK. I get a little better velocity will less powder with 8.5 than I did with 8.

That said, there are a lot of guys shooting 8 twist 6.5s.

 

[HillbillySniper]

I think you can. You don't want to spin a bullet any faster than you have to. Look at what twist the short range 30 cals are- they are using up to 18 twist barrels now. How do you think that 10 twist whisper is going to do with a 110 grain BR bullet??


I run 8.5 and 9 twists in 6.5mm. The 9 seems to do about everything short of the 140VLD and 142 Sierra. It will stabilize the 130s in my rifles. The 8.5 works with 140 Bergers and 142 SMK. I get a little better velocity will less powder with 8.5 than I did with 8.

That said, there are a lot of guys shooting 8 twist 6.5s.

No doubt you can over stabilize a slug but as far as this case an 8 twist will not over stabilize a 140gr slug. Why it matters what the whispers are using doesn't apply to the orginal question about the 6.5 barrel twist! Some of the reading I've done on other forums the 8.5 twist seems to be the best for the 140gr slugs, but there's a a lot of guys using the 8 twist barrel and doing well with it. Now you just need to make sure your not gonna wanna ever try any heavier slugs that's the only advantage I can see if you go with the 8 twist. IMO I don't think you could go wrong between the two barrel twists.

Hillbilly

 

[WYcoyote]

I'm not an expert but the guys at Benchmark Barrels recommended 1-8.5 for my 6.5-.284 Norma build with 140's.

 

[Shynloco]

In one word...ABSOLUTELY! My friend has custom rig having a Lijia Match Grade Barrel that is 1-8.5 twist. He shoots Berger 140 & 142 VLD's and his groups are incredibly tight with under 1/4MOA results shooting 5 shot groups @ 100 yds. That kinda shootin has enticed me to convert my 22-250 over to the 6.5 and install the same 1-8.5 twist Match Grade barrel.

 

[Ing. Michael W. Mayerl]

I am looking at building a 6.5 and I was wondering if an 8.5 twist can stabilize the 140 class bullets, or do you need to go to an 8 twist?

I use hammer forged barrel blanks and we have two twist length for 6,5mm:

8,6" with the inner dimensions of the CIP 6,5x55 (land diameter 6,50mm)
7,8" with the inner dimensions of the CIP 6,5x57, 6,5x65 (land diameter 6,45mm)

The 6,5x55 profile has smaller grooves so the bullet gets more deformend when pressed throw the barrel - but it rise up the barrel life.
The 6,5x57 profile has wider grooves and at the moment I start to test this in the 6,5x47 Lapua.

Important: the land diameter of the two profiles are different so a reamer with removable pilots in two diameters is necessary.


I like the 6,5èr calibers very much. They have less recoil and are able to shoot up to 1500 Meters - so no heavy sniper rifles with muzzle break in Magnum calibers are necessary to hit a long range target.

 

[texote]

So what's the heaviest bullet you can shoot with a 1:9 twist? Will a 140 not stabilize in A 6.5-284?

 

[benchracer]

I have 4 6.5's of various flavors. Three of the four have 9 twist barrels.

One has an 8 twist Krieger. The 8 twist shoots everything I have tried in it just fine. I am shooting primarily 140g AMAX's in it.

A nine twist Swede is so far the most accurate of the bunch with Berger 140g VLD's.

One of my other 9 twist rifles stacks 140g Partitions one on top of the other. I haven't done load development for the 140 AMAX's in that rifle yet, so I don't know how it will handle the longer 140's.

All of my shooting has been done in a wide range of temps from about 980' ASL to 1900' ASL.

In my own experience, the 9 twist works just find with VLD type bullets. Others have had problems, though. I would say that you likely can get by with a 9 twist, but an 8.5 or 8 twist is a safer bet.

 

[mikegaiz]

I have always used 1:8.5 with 142 SMK in my 6.5x284 and had no issues. never had a 1:9, don't know..

 

[BradY]

I consulted Walt Berger when choosing my barrel twist- he said 140 vlds should be fine in a 1:8.5 (and remembering you can push them faster than most 6.5mms) so that would work. He wouldnt comment on the hybrids though so that might be a bit much for it. 142SMKs were supposed to work as well. Honestly I went a straigh 1:8 just to be sure. I shoot at very close to sea level so take that into thought as well.

 

[savagedasher]

8.5 if your going to lean on them. Good Shooting Larry

 

[coues52]

when I talked to a few barrel makers they said for a 6.5x47 with 140's use a 1-8 ..with a 6.5 x 284 (140's)because of the faster vel a 1-8.5 would work..just what I was told..makes sense to me because of the different vel..Danny