7mm-300 win mag

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by blackaj, Mar 13, 2011.

  1. blackaj

    blackaj Well-Known Member

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    I have a 300 win mag that I'm about to re-barrel, I've been thinking about the 7mm-300 wm. does anyone have experience loading this round? How difficult is case re-forming, and is it necessary to fire form the brass. If the process of case prep is too expensive/complicated, I might consider the 7mmSTW
     
  2. LouBoyd

    LouBoyd Well-Known Member

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    What action are you using? One important part of deciding is magazine length.
    A 7mm RM has a 2.5" case 3.29" OAL
    the 300 WM has a 2.62" case 3.34" OAL
    the 7mm STW has a 2.85" case 3.65" OAL
    those lengths re SAAMI

    Any of those cartridges are only "long range" with heavy VLD bullets. When loaded properly they >will< l be longer than the SAAMI OAL. Consider the length of the magazine your rifle has. In my opinion a 3.34" magazine (as on most Win 70 standard magnums) is too short for even a 7mm Rem Mag with VLD bullets. but ok in a Rem 700 with it's standard 3.6" magazine. A Rem 700 is too short with heavy VLD bullets in a 7mm STW unless the magazine is extended, and too short for a 300 Win Mag with VLD bullets. Extended magazine are available but require a some machining of the action. I'm not saying you should or shouldn't go with the 7mm-300, but magazine length and bullet seating depth are something you should consider before making your decision. I have a 7mm STW on a 700 action with an extended magazine which I really like. A 7mm RM works well with VLDs in a standard 3.6" magazine actions too.

    What I'd like to see is 7mm cartridge based on the 7mm Rem Ultra or 300 Rem Ultra but >shortened< to the same length as the 7mm RM case for use in the Rem 700 with VLDs. I don't want it enough to go to the hassle of making reamers and dies for one rifle.
     
    Last edited: Mar 13, 2011
  3. JARHEAD1371

    JARHEAD1371 Well-Known Member

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  4. blackaj

    blackaj Well-Known Member

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    Thanks for the OAL info, I seated a round to 3.65" and it fit/cycled perfectly from my magazine (Rem 700 DM). The 7mmSTW should work fine if I went that route, any drawbacks with the STW? If I can get about 3200 FPS with 162 amax bullets I'd be happy, assuming that case life would still be good.
     
  5. Broz

    Broz Well-Known Member

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    You can get really close to that with a 7-300 win with 180's in a 28" tube. In my opinion the difference between the STW and 7/300 is Brass and throat life.
    Get some RWS brass for you 7-300 and you will be a happy hand loader. Necking down is not a big deal.

    Jeff
     
  6. blackaj

    blackaj Well-Known Member

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    Can I use a basic 7mm neck sizer to re-form my 300 win mag cases, and a 300 body sizing die? Or would I need a custom set to neck down to 7mm? Also would I need to change the shoulder angle or could I get away with just necking down. How much harder would this round be on a barrel compared to a 7mm rem mag?
    I appreciate any details you might have
     
  7. Broz

    Broz Well-Known Member

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    I don't change the shoulder angle. It is same as the 300 win case. Simply necked down. I use a 300 win bushing die and a few bushings to step it down. Once it is stepped down and fired in the 7-300 chamber I simply use the 300 bushing die with a 7mm bushing.

    If this cartridge really interests you there is a ton of info in this thread. As mentioned above

    http://www.longrangehunting.com/forums/f19/anyone-own-7mm-300-win-mag-51404/

    Jeff
     
  8. roadhunter

    roadhunter Well-Known Member

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  9. RockZ

    RockZ Well-Known Member

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    Lou,
    Sin man is doing that with the 338 initially and has plans for a 7mm version.
    Look for theads on the 338 sin.
     
  10. blackaj

    blackaj Well-Known Member

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    Thanks I've read every bit of that thread, all things said, and given how much I shoot, I think I better just go with the plain old 7mm. I only have about 150 of the 300 wm cases and most of those are on their 6th firing, seems like a good time to move on if ever.