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Thread: 300 Win Mag with 200-SIL load data needed.

  1. #1
    Boolit Master

    retread's Avatar
    Join Date
    Dec 2012

    300 Win Mag with 200-SIL load data needed.

    I am planning on using my 300 Winchester Magnum with a Rcbs 200 gr. SIL(gas checked of course) for Elk this season but all load data listings I have do not go above 190 gr. The rifle has a muzzle break so I was wondering if fouling would be a cleanup problem. Not worried about it when hunting but during load development. Any suggestion where to look. Cast pics is reflecting the 190 gr. ceiling as well as all of my Lyman Handbooks. I do powder coat as well as conventional size and lube.

  2. #2
    Boolit Master
    Join Date
    Apr 2005
    sulphur springs, Tx
    I’ll be following this with interest. I have a m 700 barrel in .300 mag and plan to rebarrel a 7 mag 700 Classic with it. Don’t know how fast the 10” twist will allow a boolit to be launched accurately; but I’d consider going with a paper patched slug
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  3. #3
    Boolit Master

    MUSTANG's Avatar
    Join Date
    Jan 2012
    Moapa, Nevada or Kalispell, Montana
    My thoughts would be to "Extrapolate" a Load from other Cartridge/Load Data.

    One such place to start might be from a thread here on Cast Boolits. See post #8 of link: http://castboolits.gunloads.com/show...ield-30-06-cal

    The text extract of that post is:

    I also have a 4 groove Remington barrel on my springfield. My load is a Lyman 311284 sized to .310, gas checked and lubed with Lyman 'Black Gold' and pushed by 31.5gns 3031 for 1740fps. These are a couple of the best 100yd benchrested groups for this year; 10 shots into .908 and the second (while going under 1MOA) has 8 shots into 1/2 MOA!

    Given the posting was for a 30-06, I believe that this might be a place to start developing a load for your RCBS 200Sil in a 300 WinMag. I have the RCBS 200Sil mold, but do not have a 300 WinMag rifle or I would give it a shot at development myself. (I probably have 200 cases of 300 WinMag brass that I've picked up at the ranges over the last few years - May pick up a 300WinMag if I see one at decent price at future Gun Show).

    "In the beginning... the patriot is a scarce man, and brave and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot." - Mark Twain.

  4. #4
    Boolit Master ammohead's Avatar
    Join Date
    Apr 2005
    McGill, NV
    Use any 190 gr load staring at the low end and work up. My lyman 49 edition shows many heavier loads for 30-06. You may find looking at that data useful. Magnum cases are harder to squeeze cast accuracy out of than say a 30-40 or 308 but it can be done. It is not going to be a situation where someone gives you a magic load and you are all set. You are going to have to find out what your rifle wants. I don't recommend starting out looking for a high velocity. Have fun. Finding your load can be more than half the hunt and there is no off season.

  5. #5
    Boolit Master Tripplebeards's Avatar
    Join Date
    Apr 2017
    Southwest, Wisconsin
    Courious to see how your boolits will stabilize and pattern going slow in a magum with a twist made for higher velocities. I tried trail boss in my 375 rum and it was like throwing gravel at my target at a 100 yards. It was all over the place with 2' plus groups using 235 gr speers. The low velocities wouldn't stabilize my jacketed bullets. My rifles wear removable brakes. If yours dose take it off and use a thread protector. It's not like the rifle is going to recoil much with cast and low velocity loads.
    Last edited by Tripplebeards; 06-17-2018 at 08:11 AM.

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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