7mm mashburn super magnum

Discussion in 'Reloading' started by Possum284, Jan 27, 2008.

  1. Possum284

    Possum284 Well-Known Member

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    Is the 7mm mashburn the same thing as a 7mm-300win I've asked other questions before but don't get much is there a reason why this isn't a popular caliber if anyone has any info it would be appreciated like were to get dies how to form cases were I can get my rifle rechambers and no I don't want an stw or dakota thanks for nay help
     
  2. James Jones

    James Jones Well-Known Member

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    I think it may be a bit bigger than the Win mag case ,I'm wanting to say that its based off of the blown out 300H&H case , similer to the 7STW. I haighly doubt that their will e enough diferance in performance to warent the cost of special ordered dies and reamer.

    The 300 win mag case necked down to 7mm would be a good one , I think it would run realy close to the STW especialy if you use Lapua brass , if you were Ackley improve it then you would likely bea the STW and do so with a shorter OAL.

    The 300 mag Lapua brass is awsome , at $1.50 a case it better be , but its as good maybe tougher than their 308 brass.
     

  3. Tbone

    Tbone Well-Known Member

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    case length?

    The 7mm Mashburn Super Magnum is based on a shortened/necked-down/blownout .300 H&H case, with the case length being 2.630", according to P.O. Ackley Handbook #1. Velocity for a 160 gr bullet was around 3200FPS. There were several other calibers based upon this length.

    The .300 Win. Mag. case comes-in at 2.620".

    Not much difference between the 2 cases in length.

    Top loads in a 7MM Weatherby w/160 grainer is approaching 3200FPS.
    Top loads in a 7STW approach 3200FPS w/160 gr.

    The not-so-popular "7MM Mashburn Magnum Long", different from any of the other 7s, used the .300 H&H case full-length, 2.850". Loads with a 160 gr. bullet duplicate the 7MM Weatherby Magnum velocities. Of course, powder selection back in those days was not as it is these days, so different velocities may be attained when using more modern powders.

    Best of luck to ya,

    Jim
     
  4. Possum284

    Possum284 Well-Known Member

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    thats kinda what my plan was just can't find much info
     
  5. biff's reloading

    biff's reloading Well-Known Member

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    gun writer Bob Hagel used a 7 msm alot and theres alot of stories about it in some of his books.
     
  6. Possum284

    Possum284 Well-Known Member

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    I am wondering if it is worth it or not what i wanted to do was have it set so I could load 180 bergers to the base of the neck and at that length the bullet woud be .025 into the lands and then i could adjust for accuracy and i figured i could get some decent velocity out if it the only down fall would be it would most likely be a single shot but with good lapua brass I should be pretty close to equaling the stw i think. sorry about the long post
     
  7. sgt.caldwell

    sgt.caldwell Member

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    I used a 7mm super mashburn magnum.

    I HAD A MASHBURM BUILT IN 1966.SHOT THE RIFLE FOR THIRTY YEARS AND WORE THE THROAT OUT.REBARRELED TO 7MM REM MAG.I STILL HAVE THE FORM DIE AND RELOADING DIES {rcbs}.also have loading data from art mashburm .brass can easlily be formed from 300 win mag.e mail me if you want any more info or dies.PS it shot 160 nosler parition at 3200 fps
     
  8. BravoLee

    BravoLee New Member

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    I own a 7mm Mashburn Super Magnum built by Mashburn Arms Company in the 60's. It was built for the late Joe DeSaye founder of J&G Rifle Ranch and has accounted for a lot of animals. He loaded it off the 300 H&H shortened, blown out, and necked down to 7mm with 160 gr Nosler Partitions at 3100 fps. I have loaded for it, shot many rounds through it, and I have found it is very tolerable of lighter weight bullets as well as heavier bullets and is an extremely accurate round. I'm currently shooting what Mr. Joe shot out of it because that old man knew exactly what he was doing.
    RCBS made a set of custom dies for him that I am using, but I'm not sure if they still make any.
     
  9. sambubba

    sambubba Well-Known Member

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    Bob Hagel said it is much easier to use the .300 Win mag cases and run them thru a forming die. You end up with a longer neck than either the .300 Winnie or the 7mm Rem mag. I use this process and currently have three of the 7mm Mash S Mag rifles. It loves IMR 7828 with Rl22 a close second. I throated mine like Hagel suggested with a 160g Nosler seated to the neck base.

    Craig
     
  10. RJ338

    RJ338 Well-Known Member

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    As the previous posters have said you can form the Mashburn Super from 300Win brass. It moves the sholder back and changes the angle to approx 32 degrees, giving you a longer neck. Only reminder is to be sure and anneal the necks after forming.
     
  11. powdr

    powdr Well-Known Member

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    I am in desperate need of a set of 7mm Mashburn Super dies. I sent a pm to Sargeant Caldwell to see if he still had his but no reply. Any info or lead on a set would be greatly appreciated. Please help! powdr
     
  12. powdr

    powdr Well-Known Member

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    Received pm today and mo will go out Monday. Thanks, powdr
     
  13. CHARLIEDUECE65

    CHARLIEDUECE65 Well-Known Member

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    Any new info on this wildcat. How do you like it, load data, specs?
     
  14. beretzs

    beretzs Well-Known Member

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    I love mine.

    The MSM has been a piece of cake to work with. FF loads do right around 3200 in my rifle.

    [​IMG]

    160 ABs run right at 3200 for me.

    [​IMG]

    They shoot pretty decent for me.

    [​IMG]

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    Same for the 160 PT's

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    175 PT's are running around 3050 or so for me.

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    Still sorting the seating depth out a little

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    Just an old beater M70 XTR I had punched out..

    [​IMG]


    This rifle has been pretty easy to work with. The 280/280 Improved and WSM are all great cartridges, but the MSM has been pretty easy to work with all in all. Responded pretty well across the board and seems to be an easy deal. I guess to me, it feels like a 7mm Rem Mag Improved. Longer neck, more case space and cases seem to last forever. I am crowding on 10 firings of my original 50 Hornady cases.