Proper Magazine Layout

Discussion in 'Gunsmithing' started by Von Gruff, Jan 31, 2017.

  1. Von Gruff

    Von Gruff GOLD SUPPORTER AH Elite

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    This is an artical I have C&P from another forum so the authorship is by Tileyman of Australia

    I originally wrote this article for our club magazine, pulled together from a few sources including Ludwig Olsen's Mauser Bolt Rifles and De Haas' Bolt Action Rifles... hope you find it useful!

    Many thousands of Mauser 98’s have been rebarrelled to a multitude of modern cartridges very different to the original 7.92mm German military chambering.

    While some of these conversions feed reliably from the magazine, many do not!

    The fault often lies with the magazine and follower profile if it is left unaltered from the original layout.

    Paul Mauser was a gifted firearms designer who carefully designed each magazine of his M98 rifles for a particular cartridge.

    Box and follower dimensions were predicated on case dimensions... Paul figured that a staggered column would enable more cartridges to fit into a given magazine well than a single vertically stacked column.

    In order to feed correctly from a staggered magazine, each cartridge needed support... from the magazine box on one side and a cartridge or the follower on the other side and underneath. With a stacking angle of 30 degrees, three stacked cartridges in contact would form the corners of an equilateral triangle:

    [​IMG]

    By multiplying the Cosine of 30 degrees ((0.866) by the case head diameter, then adding the diameter to the product of the equation, the correct magazine box width could be determined.

    For example, a 9.3x62mm case measures 11.95mm across the rim.
    So 0.866 x 11.95 = 10.35 +11.95 = 22.3mm
    Theoretically, that is the correct inside rear magazine box width for any cartridge deriving from the 9.3x62mm case.

    However, all cartridges taper, and so must the magazine.

    The same formula yields the proper box width at the point of shoulder contact:
    The shoulder diameter is 11.45mm
    So 0.866 x 11.45 = 9.92 + 11.45 = 21.4mm

    A magazine box for a 9.3x62mm cartridge must therefore theoretically taper from 22.3mm to 21.4mm. Adding an extra 0.07mm ( 0.003") or so for dirty or oversized cases makes practical sense.
    So a practical magazine box for the 9.3x62mm cartridge would taper from 22.4mm to 21.5mm

    A magazine box designed for one cartridge works for others ONLY with the same identical front and rear diameters and the same span between them. Triangles between cartridge centrelines get steep when the box is too narrow, and rounds tend to cross-stack.

    Paul Mauser also relieved the box sides slightly, from just ahead of the cartridge base to just behind the shoulder, so there would be no increase in friction between the case body and the box wall.

    He lavished equal attention on the magazine follower, which on an original M98 mirrors the box taper.

    The width of its lower shelf matches that of the case, with a 61 degree step between the upper and the lower shelf.

    [​IMG]
    The top shelf is high enough to touch the next-to-last cartridge without lifting it off the last round in the stack (its half a diameter above the lower shelf at base and shoulder) The follower has a slope to follow case taper and keep the cartridges level in the box.

    Side clearance of the follower to box is also critical.

    Followers should be about 1.5mm (0.060") narrower than their boxes so they can wriggle a bit... especially important for the last cartridge.

    A magazine follower for our 9.3x62mm example cartridge must therefore theoretically taper from 20.8mm to 19.9mm.
    A magazine follower to fit the practical box above would taper from 20.9mm to 20.0mm

    Floor plates that have been machined to hold the magazine spring tightly won't feed properly either... the springs are supposed to shimmy back and forth!

    If the spring can't shuffle a bit as the bolt strips a round, it twists and the follower tips or ends up sideways... sometimes both!

    Follower length is not as critical, but one that is too short will tend to 'dive' in the magazine box and cause misfeeds.

    Many temperamental-feeding custom rifles have had some attempt at magazine alterations, often made on trial and error rather than based on sound engineering principles.

    Getting a custom M98 rifle to feed flawlessly with a new chambering is the mark of a top-notch gunsmith who fully understands the ‘elegant simplicity’ of Paul Mauser’s original design.

    [​IMG]
     

    Attached Files:

    Last edited by a moderator: Feb 1, 2017
    Clayton, Dr Ray, CTDolan and 6 others like this.

  2. BRICKBURN

    BRICKBURN AH ENABLER SUPER MODERATOR CONTRIBUTOR LIFETIME TITANIUM BENEFACTOR AH Ambassador

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    Excellent information.
     

  3. ChrisG

    ChrisG AH Fanatic

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    This is very interesting! Thank you for sharing! I know a lot of manufacturers, especially those of cheap rifles adopt the "can't see it from my house" school of firearm assembly and as such, the magazines don't always feed reliably. It is great to know that there is a fix and an equation to figure out exact dimentions required. @Von Gruff, do you find that the fitting of the feed rails is a 'grind and then see how it works' proposition or is there a mathematical equation to how wide and how tapered the feed rails should be as well as when they should release the cartridge for optimal feeding?
     
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  4. Shootist43

    Shootist43 AH ENABLER GOLD SUPPORTER AH Legend

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    I wonder how many gunsmiths are aware of this. If all of them are and act accordingly there would never be any feeding issues on converted/rebarreled Mausers.
     

  5. Shootist43

    Shootist43 AH ENABLER GOLD SUPPORTER AH Legend

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    VonGruff, have you ever rebarreled a 1903 Springfield? It has a Mauser style action, but I'm not sure it is considered a "Mauser" action. I was wondering if the magazine layout parameters for the K98 would also apply to the Springfield. My reason for asking is that I have several Springfields and I was thinking about having one of them re-barreled to a 308 Norma Mag. I was planning on giving my gunsmith a copy of your post if in fact it is germane and or applicable.

    Another option would be for me to pick up a K98 and have it reworked.

    Your thoughts please.
     

  6. Von Gruff

    Von Gruff GOLD SUPPORTER AH Elite

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    ChrisG, it should be noted that I am not the author of the piece so my experience is only on the few rifles I have done but having said that, When I had to change the feed rails I have used the cartridge shape to determine where to grind.

    Shootist43, The magazine layout dimensions should be consistent accross the whole range of rifle types as it is the cartridge rather than the rifle that determines the stacking and feed up to the rails, except for those that use a single stack magazine. I have made a detachable double stack magazine for a bottle necked cartridge into a single stack for a straight walled cartridge but this employs different criteria.

    There is an excellent piece on making it feed on another forum with exact advise lots of pics (done by a gunsmith from the custom gunsmiths guild) but it will only get deleted if I post the link here, thanks to the forum owners "rules" so anyone wanting this resource you will have to pm me for the link.
     
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  7. CTDolan

    CTDolan AH Elite

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    This is especially important given the many wide meplat (large, flat nose) solid bullets on the market.

    @Von Gruff , thank you...wonderful share!
     
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  8. Von Gruff

    Von Gruff GOLD SUPPORTER AH Elite

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  9. Bos Javanicus

    Bos Javanicus AH Member

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    Good information there, thanks.
     

  10. CAustin

    CAustin AH ENABLER BRONZE SUPPORTER AH Ambassador

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    Interesting tutorial for those of us who are uninformed on how the action actually works.
     

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