Barrel length & twist effects

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Alfred Crouch, Jul 22, 2009.

  1. Alfred Crouch

    Alfred Crouch Well-Known Member

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    For 7 mm mags & 300 Mags - I think I heard a 26" length is needed to efficiently burn the powder. Seems I have seen that a 1:9 or 1:9.5 twist is desirable on the 7 mag.

    Remington 7 mag: mostly 26' barrel with 1 to 9.25 twist
    Savage 7 mag: 24" barrel with 1 to 9 twist
    Cooper 280 AI: 23" barrel with 1 to 10 twist

    What do you think the implications of these difference will be?
    Which would you think would be better?

    Thanks. Al Crouch
     
  2. AJ Peacock

    AJ Peacock Well-Known Member

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    I'd like the tighter twists of the Savage and Rem. for the heavier bullets I prefer (160gr and 162gr)

    My 7mm Rem Mag has a 24" barrel and I get a touch more than 3000fps with a 160gr Accubond using RL-22

    AJ
     

  3. MontanaRifleman

    MontanaRifleman Well-Known Member

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    Alfred, if you check the Berger site, you'll see the recomended twists of "their" bullets which are a longer VLD requiring a tighter twist than most conventional bullets. The 168 VLD requires a 10 twist or better and the 180 VLD requires a 9 twist or better. The Berger recommended twist is *probably* conservative. A 180 VLD would *probably* work in a 9 1/4 twist depending on velocity, barrel length, and air density. A 160 gr NAB would work in a 10 twist.

    If I was going to do a custom build, I would probably get an 8 twist or tighter for some of the longer high BC wildcat or custom bullets... especially the monometals.

    http://www.bergerbullets.com/Products/All%20Bullets.html

    Barrel length will probably boil down to about 25-30 fps per inch.

    -MR
     
    Last edited: Jul 24, 2009
  4. Alfred Crouch

    Alfred Crouch Well-Known Member

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    Thanks very much for the replies. I am learning a lot from those of you are way ahead of me traveling this road.