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What makes for a reliable mag-feed?

Discussion in 'Gunsmithing and Repairs' started by barnbwt, Nov 1, 2012.

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  1. barnbwt

    barnbwt Member

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    Is there an established way gunmakers design magazines/feed systems to ensure the design should function properly? I hear of folks with "buggy mags" tweaking feed lips, honing ramps, reshaping mag catches and all sorts of other stuff. Is there a formula to the madness, or is a brute force guess-and-check the only way to approach the problem?

    I'm contemplating converting a Steyr M95 from 8x56R to 45/70, which would require more than just rebarrelling for a repeating rifle. Other conversions attempt to use the existing feed system with similar-enough cartridges (7.62x54R and 30-40 most common). The en bloc clips used to feed the action would need to be substantially modified for the wider, shorter 45/70 round, and are themselves not very durable (disposable, even) in any case. Even successful conversions require frequent readjusting of the feed lips in the flimsy clips.

    Since 45-70 would require major clip surgery anyway, I thought it may be better to replace the innards of the entire magwell with something purpose built for the new cartridge, that would hold together much longer. That said, I have no idea where to start. If some guidelines exist for how a cartridge needs to be angled relative to the breech face, how high on the bolt face, etc. I may be able to put something together that would suffice. At least be a closer shot to a working solution, and a much more durable starting point than 100yo sheet metal disposable clips . The dream is a hi-cap using a modified Madsen or Bren mag, but I'd be equally pleased with a 4-5 shot

    Thanks for the expert advice,
    TCB
     
  2. rcmodel

    rcmodel Member in memoriam

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    Your best bet might to be to find a military rifle that uses a rimmed cartridge, like a British .303 Enfield, or a Mosin-Nagant.

    And then study that out.

    Different rifles have to feed different, depending on case rim design, push or controlled round feed, etc.

    I would not know where to begin to tell you what might be needed to feed 45-70 in a 1895 Steyr rifle.

    An even better bet would be to git rid of the Steyr and find a Siamese Mauser.
    They already will feed 45-70 with just a few minor tweaks and a barrel.

    rc
     
  3. barnbwt

    barnbwt Member

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    I have the rifle+ammo (and am waiting on the stripper clips in the mail) so I'll be able to examing exactly how the factory configuration is supposed to work. I was just curious how a "from scratch" builder (which is basically what I'll be attempting) approaches a magazine/well design.

    I suppose I'd start by duplicating the original orientation of the cartridge relative the barrel, and position it so it sticks up at the same elevation as before... Then I guess I'd place the feed ramp/guide the same distance from the tip of the round (based on OAL) as before? I dunno.

    Apparently converting these guns to 444 Marlin is more of a sure thing, but that cartridge just doesn't have the infamy of the 45-70. I'll keep looking into it, but the 444 is the second choice if I come to the conclusion the 45 is untenable. As far as why the M95? Well, there aren't too many straight-pull light rifles in big-game cartridges; thought I should do something unique for the heck of it :). I may yet decide to forego any mods entirely, if I have a religious experience or something once I finally get to shoot it in 8mmx56R :p (hurry up already, Numrich!)

    TCB

    TCB
     
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