7mm Dies w/37 deg Shoulder on 300WM Parent Case

Discussion in 'Reloading' started by chuckhammer, Jul 1, 2013.

  1. chuckhammer

    chuckhammer Well-Known Member

    Jul 13, 2010
    Had a nice conversation with Dave Kiff at PTG on Friday. I'm planning to have a reamer made for a 7mm-300 Win Mag "Improved" project gun on a Savage 110 action. He convinced me that a 37 deg shoulder would be perfect. For comparison, 300 WM and 7mm RM are 25 deg. I also plan to go with .007" less body taper than the parent 300 WM (.496" vs. .489" @ body-to-shoulder). Dave said this falls within the minimum .009" per inch of length body taper needed for reliable extraction.

    Few questions about dies:

    Neck Sizing
    I can do the initial 300--->7mm neck size reduction using a standard 7mm RM neck sizing die raised up .120" on the press to account for the longer 300 WM case. I did some trials this past weekend and it went well. Although this is a neck-only resizing die, I noticed it still has a shoulder. Since my chamber will have a 37 deg shoulder I don't believe I can use this die for neck sizing my fire-formed brass. Do the bushing-style neck dies have enough shoulder clearance to be able to re-size the entire neck of this case? If so, since the body taper is slightly reduced (case is .007" fatter at the base of the shoulder) will this prevent a typical 7mm RM or 300 WM bushing-style neck die from working with standard bushings?

    Bullet Seating
    The 7mm RM RCBS Gold Medal micrometer seating die works with a straight 7mm-300 WM since the shoulder is identical. However, with the 37 deg fire-formed shoulder, I believe this die's shoulder will prevent me from fully seating bullets. Is there a better option? I guess I can turn the die's shoulder back on a lathe but would rather find a cleaner solution.

    Body Sizing
    With the sharp 37 deg shoulder Dave tells me I may not need to ever bump the shoulder back with a body die. However, if the need does arise, I'm guessing I'll need to order a custom die? I'm not aware of any mainstream SAAMI or wildcat cartridges with a 37 deg shoulder.

    Thanks for any help you can offer.
    Last edited: Jul 1, 2013
  2. jasent

    jasent Well-Known Member

    Nov 16, 2010
    Have your gun smith make/modify you dies with your chamber reamer.