Case Base Expansion as High Pressure Sign

Discussion in 'Reloading' started by Homer, Jun 13, 2005.

  1. Homer

    Homer Member

    Feb 12, 2004
    Where do you measure a case base(25-06) - just as it begins to rebate? Is this a good indicator of pressure ? How much should it expand after firing - I have been told .005 indicates high pressure. Working up a load with 115 gr. Triple-Shocks and am at 1.5 grains over max - case base measures same before and after firing.
  2. Mysticplayer

    Mysticplayer Writers Guild

    Jul 27, 2001
    Measure within 1/8" of the extractor groove. The big thing is be consistent. How much is a very dangerous question because of all the variables in a chamber.

    Best thing is to shoot factory ammo with the same brand of brass you are using. Better is to sample a few and compare.

    Measure what the expansion is. Compare to your load. This only works for new virgin brass. Measuring expansion on once or multi fired brass will give the wrong results.

    Also, compare to muzzle velocity. If more then 100fps above listed max vel, back off. Then there is primer flattening, etc, etc.