308 overpressure

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by Tim-o-thy, May 9, 2019.

  1. Trevor60


    May 24, 2010
    Good Afternoon

    There are a number of variables which will affect pressure and velocities.
    --To be safe you should always follow reloading manual numbers

    Here is a variable

    Pg 148
    Effects of Seating Depth / COAL on Pressure and Velocity The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well-known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.

  2. Don_Parsons


    Nov 27, 2017
    I find the nodes before I magospeed.

    178 ELD-X & M @ 43.5 Varget from a 32" barrel with 10 1/4 twist...

    My other 308 likes 42.9 gr Varget with same 178 grain'ers.

    Velocity means nothing to me if I don't get good groups.

    The ELD series of bullets still get frontal expansion as low as 1300 ft-per seconds,,, I don't like to see lower than 1600 to be on the safe side...

    Good luck as you find the magic load
    Dgd6mm and Zero333 like this.
  3. Zero333

    Zero333 Silver $$ Contributor

    Dec 24, 2015
    2,600 fps from 18"bbl with 178's is right up there.

    The other issue is new brass relieves some of the initial pressure by having to fireform. I've had this issue with 308win Large primer Lapua brass.

    I suggest full length sizing with about 0.003" shoulder bump and taking it easy for the first few firings.

    You should have a solid load around 43 - 43.5 gr of Varget. Nevermind the ES/SD unless you're shooting beyond 600 yards.
  4. esromvre1


    Jul 2, 2010
    Ran into the same problem. For me it was case lingth

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