Stepping down brass for 7mm-300wm

Discussion in 'Reloading' started by BigSwede, Aug 24, 2015.

  1. BigSwede

    BigSwede Well-Known Member

    Messages:
    426
    Joined:
    Aug 2, 2014
    New build with benchmark m24 8.5 twist at 28" in an HS stock. My Chamber cast neck measures .3175. I have Rcbs gold medal full length bushing dies. I have .330, .325, .315 and .314 neck bushings. I had a hand full of used rem brass. I bumped the shoulder and stepped the neck down with 330, 325, and borrowed .310. (315,314 hadn't come in yet). Anticipation was killin me. Put cruddy 18x scope on and I fired first 3 berger 180's at 400yds and they were a 2.5" triangle. Ok we got potential. My question is in the brass preparation..... <<<Should I trim, chamfer and debur my brass (new winny brass now) before I step it down or after for optimum accuracy?>>>any other brass prep advice on this cartridge welcome.
    Thanks, -Swede
     
  2. Wachsmann

    Wachsmann Well-Known Member

    Messages:
    653
    Joined:
    Feb 1, 2008
    I don't have any experience with that caliber but I resize my brass first, clean, then do any trimming if needed and last do my VLD reaming and deburing last. This has pretty much been my usual routine for quite some time. I don't see If I had any other caliber that I would change up unless there was some neck turning that had to be down. Then that might come somewhere after resizing I would think.
     
  3. BigSwede

    BigSwede Well-Known Member

    Messages:
    426
    Joined:
    Aug 2, 2014
    Thanks for the response. Geuss I'll trim chamfer and debur before stepping down. If I give the brass a varsity effort maybe I'll be rewarded at the 1000 ++ mark.
     
  4. rickiesrevenge

    rickiesrevenge Well-Known Member

    Messages:
    169
    Joined:
    Apr 14, 2015
    I wouldn't trim before you neck them down. Run them over an expander to make them round, chamfer, and then size them down. Sometimes when you neck cases down the case mouth becomes a bit uneven. I'd fire them once before you trim them too.

    Aaron
     
  5. BigSwede

    BigSwede Well-Known Member

    Messages:
    426
    Joined:
    Aug 2, 2014
    Thanks Aaron...
    --I have weight sorted them, run them over expander to round them out, and now I have to step them down with three bushings. My thoughts were perhaps if I trim and chamfer first them they would be "worked" more evenly which I'd think would create a more uniform neck tension on the bullet. Am I way off on this ? Is this unnecessary?
    -Swede
     
  6. MagnumManiac

    MagnumManiac Well-Known Member

    Messages:
    1,414
    Joined:
    Feb 25, 2008
    I would neck them down before I did anything, then chamfer, load and shoot.
    I don't do any load testing, trimming or sorting until the brass is fireformed for my chamber, unless it requires neck turning first.
    I square all necks by running them through a minimum neck die, uniform and chamfer flash holes, load and shoot new brass. Only after this do I anneal, set proper neck tension, trim and turn if required.
    Going down in calibre can thicken necks some, not always, but a good idea is to measure them before and after, just to be sure.
    Hope this helps.

    Cheers.
    gun)
     
  7. BigSwede

    BigSwede Well-Known Member

    Messages:
    426
    Joined:
    Aug 2, 2014
    Sound advice. That's what's makes this site enjoyable. Thankyou

    -Swede