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Thread: 300 Win Mag case's converted?

  1. #1
    Boolit Bub
    Join Date
    Nov 2013
    Location
    Paxton, Il
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    68

    300 Win Mag case's converted?

    I did some trading for some 45-70 brass and with it came some Herters and WW 300 Mag case's that were straight wall. 2.5" long with an internal dia. of .458. I'm thinking they were fire formed but was wondering what they were loaded for. Anyone have an idea?
    I did some checking and they were probably used as 458 Win Mag brass.

  2. #2
    Boolit Grand Master


    stubshaft's Avatar
    Join Date
    Apr 2009
    Location
    Southernmost State of the Union
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    5,854
    More likely than not it was a 458 Win Mag. I tried to fireform some 338 WM cases and they came out shorter than I wanted, the 300 WM's came out perfectly. I used 12 grs. of Red Dot and COW filler with a toilet paper plug.
    Old enough to know better, young enough to do it anyway!

    Men who don't understand women fall into two categories: bachelors and husbands!

  3. #3
    Boolit Master 15meter's Avatar
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    Feb 2017
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    SE Michigan
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    2,508
    Most likely .458 Winchester Magnums. I did that conversion last year. I even wrote it up on here. Not the easiest fire forming, it took several tries to get it right. But it can be made to work.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check