300wm headspace

Discussion in 'Reloading' started by shocking300, Feb 19, 2012.

  1. shocking300

    shocking300 Well-Known Member

    Jan 31, 2012
    I shot some factory ammo, and measured unfired brass vs the brass i just shot and it grew by .0025 and it freaked me out, the question is; is the factory brass that much shorter or my headspace is to long, the rifle is Remington 5r Millspec 300wm and has 550 rounds fired, 77gr H1000 208AMAX, no sign of over pressure. Thanks
  2. AtownBcat

    AtownBcat Well-Known Member

    Feb 3, 2009
    I am learning a lot about headspace myself, but I can tell you your numbers are in line with everything I have seen. Even virgin brass bought to handload is set back .020. Something about factory ammo having to fit in the smallest chamber out there so they make it this way to cover their ass...

  3. AZShooter

    AZShooter Well-Known Member

    Dec 12, 2005
    That is a small amount. My friend and I both had 300 win mags. Mine was a post 64 push feed model 70 westerner and his was a Mark X. I was asked to load for his rifle. I took my partially FL sized brass and couldn't even get his bolt close to the point where it might be cammed over. My chamber was long and his was short. I have read that the chamber's shoulder area can vary quite a bit in belted magnums but never realized it till it happened to me. FYI the brass lasted for five firings with careful partiaL FL sizing. I felt that was enough firings considering the circumstances.