208gr A-max, 1 in 10 Twist

Discussion in 'The Ammo & Reloading Forum' started by The_Rifleman, Mar 10, 2010.

  1. The_Rifleman

    The_Rifleman New Member

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    Ohio
    Howa 1500 30-06, 1 in 10 Twist, 22" Barrel.

    My load development targets only shown one node, (which is weird,) with the 208gr A-maxes; but that node proved to be a little too hot for my liking so I reduced my load to the next best kinda node.

    Those cartridges never seemed to hit very tight at 400 yards. I would hit the 8 x 12" target but almost always right on the edge and/or high. It could be me.

    So I shot a group today at 300 yards with that load , I came up with a group much like the node size, (1.16moa,) but the group is weird, (tall,) so my technique could have been flawed. The shots, including my fouling shot all were within 1.25" wide, which had me wondering if I was to blame.

    It could be me, or my new bean bag, or seating depth, or twist rate.
    I've addressed the bean bag... Now I need to know if anyone has got sub-moa accuracy with the 208gr A-Maxes with a 1 in 10 twist, (or greater,) before I load some cartridges at various seating depths.

    I shoot the Hornady 220gr RN bullets at .625moa at 400 yards so that makes me think that seating depth is the cure.
    Although, the A-max is 1/4 inch longer.

    Here is the 30 second video of my fouling shot then group.
    208gr A-Max, 300 Yard Group
  2. LDBennett

    LDBennett Well-Known Member

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    Did you apply the Greenhill formula to see if your 1 in 10 inch twist rate is fast enough for such a long bullet for a 308 bore?

    http://en.wikipedia.org/wiki/Twist_rate#Twist_rate

    Get the twist too slow and the bullet will not stabilize. Off hand without doing the calculation, I would think your barrel twist is too slow (???) but only doing the math will tell you for sure.

    What's this "node" you are talking about???? I've not heard this expression in regards to anything else you mentioned.

    LDBennett
  3. The_Rifleman

    The_Rifleman New Member

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    I never heard of the Greenhill formula, thanks!
    I had to find a calculator since I don't understand the chicken scratch. ;)
    Calculate barrel twist rates. FREE!
    I need a 1 in 9. :(
    Thanks!


    I was talking about the Audette Ladder Test and the accuracy nodes I wasn't getting.
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