Idea for a 7mm Wildcat

Discussion in 'Reloading' started by rdm, Sep 14, 2013.

  1. rdm

    rdm Well-Known Member

    Messages:
    62
    Joined:
    Jan 25, 2003
    Has anyone tried cutting the RUM family of cartridges brass down to around 2.500" and keeping the shoulder at the current 30 degrees and then necking it to 7mm with a neck length of .330"?


    Should be about the same as the 7mm Dakota and 7mm STW.
     
  2. benchracer

    benchracer Well-Known Member

    Messages:
    1,348
    Joined:
    Dec 18, 2009
    What you are talking about is the long way around to a 7mm/.375 Ruger, which would have slightly more case capacity than something on a cut down RUM case.
     

  3. cowboywhorses

    cowboywhorses Well-Known Member

    Messages:
    477
    Joined:
    Mar 14, 2010
    Just a note ! !

    I am doing a 7/338 Norma Mag on a 35 degree design.

    Using 300 Norma as a parent case.

    Do like the 7mm / 375 Ruger look.

    Good Luck and God Bless

    Jeff
     
  4. backwoods83

    backwoods83 Well-Known Member

    Messages:
    2,206
    Joined:
    Jan 8, 2011
    It might have a 3 or 4 grain increase over the 7x375R, because of the .550 base vs .532 with both having about the same taper, the long and short is that you stand to gain virtually nothing except a hell of a lot of extra work for no good reason.
     
  5. rdm

    rdm Well-Known Member

    Messages:
    62
    Joined:
    Jan 25, 2003
    I think the Dakota is almost perfect...Except for that rim diameter forcing the need to open up the bolt face.
     
  6. 7mmRHB

    7mmRHB Well-Known Member

    Messages:
    338
    Joined:
    Jan 12, 2005
    RDM, I did the very cartridge you're asking about back in 1999 before these other brass options were available. The Dakota brass was crap back then but has been upgraded since about 2006. My cartridge case is 2.555" with 35* shoulder and reduced taper. It's called the 7mmRHB and performs very well. 3200fps and 1/3 moa @ 1K with 180 Bergers. You need a set of form dies and be capable of annealing and neck turning to form this case.

    As others have pointed out it is a time consuming way to get to where you would be by necking down a 300 Dakota to 7mm. I designed the 284 STAK which was the 300 Dakota necked to 7mm with a 40* shoulder and reduced taper. It's performance is nearly identical to the 7mmRHB but very easy to make.

    The 7mm Dakota is a smaller case than the 300 Dakota ( about 7 grs) The improved 284 STAK holds 3 - 4 gr. less powder than the 7mm RHB even though it is the same length. It is smaller in the body by .003 or .004 depending on the lot.

    Good luck with your project. PM me if you would like more info. ---- RHB
     
  7. trueblue

    trueblue Well-Known Member

    Messages:
    2,123
    Joined:
    Feb 18, 2008
    Jeff
    Look up the 284 Jazz, for load data info
     
  8. 7mmRHB

    7mmRHB Well-Known Member

    Messages:
    338
    Joined:
    Jan 12, 2005
    The 375 Ruger case is way smaller in diameter than the Dakota case. ( .532 - .542 )and the RUM case is .545.I'd bet the 375 case is actually even smaller at the web than what the drawings show, which is pretty normal! The 375 is a little longer but not enough to make up for all the volume lost through the much smaller diameter. I don't know what kind of velocity the Ruger case would achieve , given equal pressures, in comparison to the STAK or RHB cases. --- RHB
     
  9. Rocky Mountain

    Rocky Mountain Well-Known Member

    Messages:
    385
    Joined:
    Sep 13, 2010
    7mm - 300 Blazer :D
     
  10. JARHEAD1371

    JARHEAD1371 Well-Known Member

    Messages:
    676
    Joined:
    Oct 9, 2008
    I'm planning on building one very similar to yours, just not sure of the reamer just yet. I've been reading a lot about what GAP has been doing with the 6.5 SAUM, and I think this will be a larger version of it. I'm wanting 3050-3100 fps, with the 190 gr Matrix, and 26" barrel. I'm thinking it will be a fairly light load (psi) for much longer barrel life. Be sure and post your rifle and load after it's finished.