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Thread: 450 Marlin bolt gun

  1. #1

    Default 450 Marlin bolt gun

    I am in the process of picking up another all weather Ruger 77 in 350 mag. My sole purpose for this gun will be to send it off to Montana Rifleman for a new barrel in 450 Marlin.

    I have grown quite fond of the Speer 350gr Hot Core bullet and will be building this rifle around that bullet. I am going to go with a 20 inch barrel of 1 in 20 twist or there about.

    The Ruger 77 is capable of withstanding a 25% increase in CPU's over the Marlin 1895 that this cartridge was designed for. My question is what percentage of an increase in velocity does this translate into? Since the Marlin at 42,000 CPU is producing just over 2000fps, would it be reasonable to think that at least with the light 350 gr Hot Core that it would be nipping at the heels of the 458 Win mag when fired from a chamber pressure of around 52,000 CPU? I know the velocity is not going to increase in direct % to the CPU's.

    Anybody done a bolt gun in 450 Marlin?

  2. #2


    Nope, but it's a good idea. Siamese Mausers for conversion to a bolt 45-70 are getting hard to find and expensive. The one I owned and the others I've seen or tried never came off as well as I thought they should. The M77 action would suit me a lot better, and is certainly a lot more available these days.

    As for gains, I'm not sure how much you would gain over a Siamese 45-70. I wish I could find my logs cuzz memory fades, but I sequentially owned a 458 American 2" and the Siamese 45-70. Foggy fogey memory tells me that I got similar ballistics from the two. I'm just not sure there's enough case capacity advantage of the 450 over the 45-70 to make the difference, and I don't think you could push the pressures all that much higher with the new case. I'm ready to be proved wrong on all counts, because I think the M77 conversion to 450 has a lot more potential today than snorting around to find a suitable Siamese for another 45-70 conversion. Might as well go with the newer action and case and get it over with. In my experience anyway nostalgia isn't a strong enough reason to ever do another Siamese conversion.

    That's sure the route I'd go before pooping as much pressure out of a Marlin 45-70 as is done today, in spite of the way Marlin rates their own action strength. The M77 is stronger, and that's what I'd reach for before I'd ever hotrod a Marlin to similar pressures.

  3. #3

    Default LOL;Marlin

    To get a very good estimate of the velocity of the rifle and ammo you wish to load. LOOK in the Cartridges of the World book under .458 x2" Barnes/American. The round has been around for years, just had a belt change and a new name for the lever gun.
    IT AIN'T NEW, just has a new wrapper/name.
    Also chamber pressure in measured in CUP (not CPU) or PSI, Black powder is LUP usually.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

  4. #4



  5. #5

    Default cost

    how much do you expect the barrel conversion to be?

    forty below

  6. #6


    These folks installed a SS 458 win mag barrel on 77 magnum action for me a couple of years ago and including lapping and squaring the action it ran $450 if my memory serves me right. Inflation figured in its probably a little over $500 now.

  7. #7
    Member KRS's Avatar
    Join Date
    Feb 2007


    Hornady LeverEvolution ammo.... I haven't seen any better ballistics than those !

    325 grain is the only offering, zero at 150 yds, 3" high at 100, 2.2" low at 200, 250 is about the limit... 300 yds is a 22" drop or so.


  8. #8
    Member .338-06's Avatar
    Join Date
    Apr 2006


    If anyone is looking for a Siamese Mauser to convert, I have a good one I'm willing to part with. This is an orginal, not an action converted to .45-70.


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