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Thread: 375 H&H to 300 H&H

  1. #1
    Boolit Buddy
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    375 H&H to 300 H&H

    I have about 200 375 H&H cases and no rifle to suit, but I do have a rifle in 300 H&H, I have never tried too make brass shrink down would it be as simple as annealing the brass and running it through a 300 sizing die or would it require a few more steps I'm open for any advise.

  2. #2
    Boolit Buddy
    zarrinvz24's Avatar
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    Your going to have to turn the necks as well. If it were me, I would try and find someone to trade with before committing to that type of case forming.

  3. #3
    Boolit Master
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    My mate ran them through his sizing die to bring them down and never had to neck turn, but I would not fire any of his reload to save my life as his idea of a compressed load was using a dowel and hammer to force powder down to give space for more. Sell the brass and buy 300 Hand H your rifle will love you for it. Regards Stephen

  4. #4
    Boolit Master
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    Sure, it can be done but, I bet zarrin is right, you'll have to turn the necks. I also wouldn't anneal first as I suspect you'll collapse more shoulders than you'll end up with finished cases. It would be sort of a fun project if you were just looking for something to consume time. Better bet is find someone to trade or just buy 300 H&H brass.....if you can find any. I have no idea its availability.
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  5. #5
    Boolit Master 15meter's Avatar
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    Actually having converted 375 H&H to 300 H&H, I anneal AFTER reforming.

    Neck turning is on a rifle by rifle basis. For the Rigby rifle I was forming the brass for I didn't have to neck turn.

    It is a fairly easy conversion. I use Imperial wax, into the die an eighth of an inch, back out give the case a slight turn and back in another eighth of an inch. Continue until the case is fully formed. You'll want to add a little more lube half way through the sizing.

    If the cases don't chamber well after F/L sizing, I'll make one last pass through the sizer die using a shellholder with 5-10 thousands ground off the top. Then fire form in the rifle.

    With that long tapered shoulder you probably won't have to do that. I don't remember if I had to do it for the 300 H&H, most certainly did when forming 7x61 Sharpe and Hart.

    Sharper the shoulder, more likely you'll need to push that shoulder back a little more for first firing.

    I've done 375 Weatherby to 300 H&H, that's the tough one, Weatherby brass is strong stuff.
    Last edited by 15meter; 07-20-2021 at 07:42 AM.

  6. #6
    Boolit Buddy
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    Thank you one and all for your help.

  7. #7
    Boolit Master
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    Buy a .375 H & H !
    There are only two kinds of men:

    1. Those who know Jesus Christ is both Creator and Sovereign Lord.

    2. Those about to learn that Jesus Christ is both Creator and Sovereign Lord.

  8. #8
    Boolit Master


    GregLaROCHE's Avatar
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    Quote Originally Posted by wmitty View Post
    Buy a .375 H & H !
    You beat me to it. Best solution is to buy a .375 H&H!

    Otherwise you are probably better off trading or selling it if you can. Maybe you can find some .300 brass here. Post something in the WTB section, as well as the want to trade or sell sections.

  9. #9
    Boolit Master
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    Run one through your sizer and seat a bullet then measure the neck and see how it compares to a 300 case fired in your rifle. You will probably have to neck turn it. I tried firing one in my 300 without neck sizing and pressure was excessive.

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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