12 twist barrel max bullet size?

Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by Lefty Trigger, Nov 8, 2019.

  1. Lefty Trigger

    Lefty Trigger Gold $$ Contributor

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    Looking at a new 308 barrel in 12 twist and it has a "match" chamber for shooting 155 grain bullets. what would be a max weight/length for a 12 twist? Will it shoot 168's. Going over to Bergers site now to run some numbers before I buy the new barrel.
     
  2. bpd459

    bpd459 Gold $$ Contributor

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    Greetings,
    Berger 185 Juggernauts shoot just fine in a 1-12 twist. Don't forget the 190gr SMK.
    John
     
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  3. joed49

    joed49

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    I have a 1:12 twist, 185 gr Berger VLD Targets shoot just fine from it. Many told me 168 gr would be the limit but never had a problem.
     
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  4. Kurz

    Kurz

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    Remember that the rule for choosing twist rate is to pick the slowest twist which will stabilize the bullet you choose to shoot. Then when you run your numbers against the Berger Stability software, remember that if you are slightly below their 1.5 number that your bullet IS NOT unstable, you are simply losing BC and you need to shoot in your true BC anyway before running your drop/drift charts. :D
     
  5. FrankG

    FrankG

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    Up to most 190gr bullets will fly in a 12 twist with no issues.

    Starting shooting solids in the same bullet per say and you can start having issues. The solids in the same weight as a conventional lead core/copper jacket bullet the solids are typically longer. Length of the bullet usually dictates more of the twist needed then bullet weight.

    Later, Frank
    Bartlein Barrels
     
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  6. r bose

    r bose

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    For this "match chamber" I'd be more concerned with the length to the lands. In a "palma" chamber the 155 sierra 2155 is just over 2.750 OAL just at 20K off the lands. So, a 185g projectile is going to be WAY DOWN in the case unless you plan on throating out the lands.
     
  7. Lefty Trigger

    Lefty Trigger Gold $$ Contributor

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    I'm pretty sure its a match chamber because it is for the 155gr Palma bullets. I want to play with them anyway so that's ok but was curious if it would shoot heavier bullets as well. Probably never above 175gr and a short throat should not cause issue if I back the loads down because of seating depth. Playing with Bergers stability calculator proved interesting, some larger bullets are "stable" but their own 155gr is not, weird? They claim their 155 needs a 11.5 twist, I know that is not gospel but it has shown some interesting results...
     
  8. WAMBO

    WAMBO Silver $$ Contributor

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    My factory Rem 700 has a 1-12" twist and it shoots the longer 175 SMK sub MOA at 1000 yards, the 168 SMK has left full profile side ways bullet holes in the target but are fine at 600yds.
    I wouldn't have any regrets using that twist for up to a 175gr bullet.
     
  9. 4xforfun

    4xforfun Gold $$ Contributor

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    I have won lots of wood at 1K with 200 Hybrids and a 12 twist in my WSM.

    Tod
     
  10. NZ_Fclass

    NZ_Fclass

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    Although the trend is for "long for weight" bullets... I shoot 165g in a 13 twist for F-class. No stability issues - nor with 168 Hornady. Not long ago, one of the members was using 175 match Kings in a 13 twist too. If the gun has been smithed properly, and concentric, it will often handle bullets longer than the paperwork suggests. providing speed is maintained, I guess that is why 4xforfun can shoot 200's in a 12 twist successfully. Note - my next barrel will be an 10 or 11 twist, to ensure good stability at reasonable load speeds. May all your 9's be 10's.
     
  11. Ned Ludd

    Ned Ludd Gold $$ Contributor

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    Lefty - do you by any chance have the print/specs for the reamer that was used to chamber this rifle? I have a couple rifles that are probably chambered similarly to your setup, maybe with just a bit more freebore (0.085" fb). In the past, I have sometimes been able to get away with 185 Jugs in a chamber cut with that particular reamer, sometimes not. When it worked, the Jugs were seated pretty deep in the neck, with the boattail/bearing surface junction just at, or barely above, the neck/shoulder junction. In a recent re-barrel, my current Lot# of Jugs just aren't cutting it in that chamber, too much pressure and insufficient velocity. However, the Berger 168 Hybrids and 175 OTMs are shooting like champs. Either should work with a 12-twist barrel. I'm particularly fond of the 168 Hybrid, very high BC relative to its weight, and very good precision.
     
  12. Lefty Trigger

    Lefty Trigger Gold $$ Contributor

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    Sorry no I don't have the print. I have ordered the barrel and will see how it shoots. My plan is mostly the 155's or 168's because my longest range is 300 yards so ultra high BC bullets are not really going to be of any great benefit at such a short range. Been hoping to get on a longer range but nothing is close or easy to shoot on unless your a member and its hard to be a member if the range is 3 1/2 hours away.
     

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