Effect of long throat on M.V.

Discussion in 'Reloading' started by Topshot, Oct 24, 2009.

  1. Topshot

    Topshot Well-Known Member

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    Nov 3, 2008
    With the new .338 Edge rifle I just had built with a 30" barrel. I asked for a long throat to seat the 300 grain SMK bullet out so that the base of the straight shank was level with the bottom of the base of the neck.

    I figured this would give me more Powder capacity as the projectile is not encroaching into the powder area. This also means that I single load my rifle with the bullet seated so far out as it will not fit into the magazine. Cartridge OAL is 3.975" and I could go to 4.000" before I touch the lands.

    Well with a "standard" load of 92gn of H1000 I am getting 2756 fps which I think is below what most .338 Edge rifles will deliver.

    However, as I have plenty of powder capacity, I can put in 97gn of H1000 before I get pressure signs with primers that are just starting to flatten and the velocity is 2958 fps.

    Is this a normal thing to observe with a long throated chamber and the bullets seated out further?
     
  2. Ridge Runner

    Ridge Runner Well-Known Member

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    Dec 13, 2002
    perfectly normal, since you have a long throat you have effectively enlarged the chamber, with a larger chamber it takes more powder to create the same pressure/muzzle velocities.
    RR