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Slugging the bore question?

Discussion in 'Ammunition & Reloading' started by taylor, Apr 22, 2012.

  1. taylor

    taylor Willamette Valley Well-Known Member

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    Aren't the lands more important? don't the grooves just show how much depth the bullet can expand?
    For instance I have heard of people with Tokarev's who slug the barrel and measure the grooves and get a .311 or .312 and freak out saying" the Tokarev is supposed to have a .308 barrel and mine is oversized!"
    Ideally if a bore is supposed to be .308 shouldn't the grooves be .002 or .003 more?
    If a bore(lands) is .308 should I buy bullets for .308 or .309 or what?
     
  2. Mark W.

    Mark W. Silverton, OR Bronze Supporter Bronze Supporter

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    NO if the bottom of the grooves is larger then the diameter of bullet then the gases will excape past the bullet.

    Unless the bullet is a Mini ball design with a thin rear shirt and a hollow center it will not expand much at all.

    SO thats the problem with a .308 bullet in a 7.62mm bore which actually measures .311-.312.


    You would measure the ridges on a test slug to determine the diameter of bullet best suited to your bore. NOT the GROOVES ON THE BULLET. And then oppisite if you were measuring in the bore.
     
  3. taylor

    taylor Willamette Valley Well-Known Member

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    I got them mixed up, so a .308 pistol barrel should measure .308 straight across from groove to groove? that would be the bore size?
     
  4. Mark W.

    Mark W. Silverton, OR Bronze Supporter Bronze Supporter

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    YES
     
  5. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    You'd be amazed at how much a bullet will expand (obturate) when fired in an oversize barrel. When there's 50,000-60,000 psi behind it, all at once, the plastic limits of the bullet material (lead and copper) have been exceeded multifold. About the only bullets that don't are the "Solids" like Barnes.

    Naturally, this is dependent on the gap not being all that excessive but a few thousandth's will definitely disappear when the charge goes off.