New 6mm AI barrel twist?

[46and2]

I'm ordering a new sporter barrel for bean field deer, varmint hunting. I plan on using 105 Hybrids, 105vld, 105 Berger boat tails or 112 Matchburners. I'm torn between ordering a 7.5 or 8 twist barrel.

I'd like to get an eight twist barrel but Bergers twist rate calculator says I'll be marginal with the 112gr and 105 Hybrids.

Since I have no way of knowing which bullet the barrel will like. I don't want a twist so fast that I start having jacket failure in 500 rounds. My last 6ai could push 105gr bullet to 3400 fps with Rl26!

Should I just go with 8 twist and hope for the best?

 

[urbanrifleman]

In an 8 twist you hit 300k at 3500 rpm. That's the rpm limit. I'm not sure what the deal is with that Berger calculator. It's almost like it's telling you to shoot bullets past the terminal limit.

3400 fps with an 8 twist is optimal spin.

 

[dgeesaman]

To be clear you’re talking about 6mm Remington and not one of the 6BRs?

 

[Liven The Dream]

I ran a 6 Remington 1-7.5 Prone Rifle with 115 D-tacks at 3025. Very Fun Rifle for a Short Time.\
1725 Rounds No Throat .

 

[dakor]

I'm ordering a new sporter barrel for bean field deer, varmint hunting. I plan on using 105 Hybrids, 105vld, 105 Berger boat tails or 112 Matchburners. I'm torn between ordering a 7.5 or 8 twist barrel.

I'd like to get an eight twist barrel but Bergers twist rate calculator says I'll be marginal with the 112gr and 105 Hybrids.

Since I have no way of knowing which bullet the barrel will like. I don't want a twist so fast that I start having jacket failure in 500 rounds. My last 6ai could push 105gr bullet to 3400 fps with Rl26!

Should I just go with 8 twist and hope for the best?

I would get an 8 twist. Bergers calc is not accurate from any of the real world experiences I have had.

My first 6-284 barrel was a 9 twist and it shot 105 bergers even down to -32 below zero out to 1100 yards very accurate.

If you put my load data of 3353fps with a 9 twist at 865ft with a temp of even 20 degrees it says its not stable.

Well its wrong. I ran that load for years and never had any issues and shot many animals with it and 1/4 MOA groups at distance on many cold days.

 

[SteveOak]

Berger's twist rate declarations are VERY conservative.

I suppose you can find the complete explanation if you dig enough but the number they give is to absolutely ensure NO BC is lost, not that the bullet might be 'unstable' at 1.49999.

Unless you can't afford to give up 1 or 2% of the BC, it is not necessary to achieve the 1.5 'stability factor'.

 

[AlNyhus]

A couple things:
-Run the bullet with JBM's stability calc.
-If the barrel mfg shows both .236 and .237 bores, check the '.237 bore'.

 

[ELR LVR]

I'm ordering a new sporter barrel for bean field deer, varmint hunting. I plan on using 105 Hybrids, 105vld, 105 Berger boat tails or 112 Matchburners. I'm torn between ordering a 7.5 or 8 twist barrel.

I'd like to get an eight twist barrel but Bergers twist rate calculator says I'll be marginal with the 112gr and 105 Hybrids.

Since I have no way of knowing which bullet the barrel will like. I don't want a twist so fast that I start having jacket failure in 500 rounds. My last 6ai could push 105gr bullet to 3400 fps with Rl26!

Should I just go with 8 twist and hope for the best?

8 twist should work fine
I use an 8 in my 6x284 which should be similar in velocity.
Stabilizes the heaviest bullets up to 115 gr
I think I ran the numbers and SG was like 1.4 or something, cant remember for sure but was fine for accurate shots out to 2200 yds, ( havent tried past that distance yet)
-------------
As an aside I used to use a 1:9 with 107 SMK's and even that stabilized just fine even though theoretically it was marginally stable, and made shots out to a mile with it.

 

[Liven The Dream]

Old say from Barrel Maker Guy Jack in Wisconsin.
" More Twist Better".
My Dasher are 1-7.5 one .236 not as good as.237 ?? slower.
6 BR 1-8 OK but makes think would a 1-7.5 work Better ?? Time will tell.
Will give it a 600 yard E-target test soon.

I only shoot 105HB and 109HB in my Dashers

 

[46and2]

To be clear you’re talking about 6mm Remington and not one of the 6BRs?

Yes sir, 6mm Remington Ackley Improved.

I still have 400 pieces of Norma 7×57 Mauser brass from my last barrel. I must have been bored at one point because they're already sized and neck turned. Lol.
Good brass by the way. The last batch had seven firings and the primer pocket still measure. 208".

 

[Idaho-Lefty]

In my 24", 6 XC, the 1-7.5 Twist, shoots everything from, 80 gr. to 110 grain, Bullets,.. very WELL !
I too wanted, an 8 twist ( they were, very SCARCE, during the Covid era ) But, am quite Happy with, the 7.5 twist !
5 shot, "BugHoles", in the 2's and 3's are,.. common except with, 87 gr. V-Maxes for, some reason !
IMO,.. Get the 1-7.5 twist to Be,."SAFE" with All of, the Heavier Bullets.
Don't go "Too Crazy" on Velocity with, the Lighter Bullets, tho ! ( Some May, come apart or, NOT shoot, well )

 

[DaveTooley]

I've shot bullets with an Sg of 1.1 with no problems. 1.5 is very conservative.