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Thread: Sten tubes

  1. #11
    Gunco Veteran Frogman's Avatar
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    You could go with the larger O.D. receiver if you weld in a blocking pin and a corresponding
    alteration on the bolt. That's how the PPSH 43-c semi was done.
    "The two enemies of the people are criminals and goverment, so let us tie the second down with the chains of the Constitution so that the second will not become the legal version of the first" ~ Thomas Jefferson

  2. #12
    Gunco Regular Shooter17's Avatar
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    There are several versions of the semi auto Sten builds.

    When it comes to the FCG and bolt modifications, you will need to decide if you want striker fired or hammer fired.

    Then there is pistol vs rifle and traditional vs vertical mag feed options.

    Other than installing a denial pin or block to prevent installing an unmodified butt stock, the pistol build is the simplest, as it does not require 922r compliance.


    Shooter

  3. #13
    Gunco Member grumpy7mag's Avatar
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    Any info would help. The goal is a modern version with better trigger,different caliber,tacticool factor. Which brings up a point. Are there any formulas to figure out bolt weight for different calibers?

  4. #14
    Gunco Regular Shooter17's Avatar
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    Here are some calculations/formula for bolt weight and travel.


    Calculating a blow-back bolt weight for a maximum/safe bolt push back from ballistic parameters:
    ---------------------------------------------------------------------------
    Bolt weight = 0.5* (V / Sv *Eb) * (bW / 7000)
    ---------------------------------------------------------------------------
    Ballistic performance parameters:
    bW = bullet weight (grain)
    V = Velocity (ft/s)
    Cartridge specifications:
    buA = Bullet diameter
    nA = Cartridge neck diameter
    baA = Cartridge base diameter
    Eb = Effective bullet/base = (buA / (baA-nA+buA))^2

    Blowback setting Sv:
    Sv = Bolt push back speed = 6 ft/s

    -----------------------------------------------------------------------
    Examples from values taken from WiKiís ammo info pages:

    Cartridge type bW V nA baA buA Eb Bolt weight (lb)
    0.22 LR 40.00 1080 5.70 5.70 5.70 1.00 0.51
    9mm Nato 115.00 1300 9.65 9.93 9.00 0.94 1.78
    .45 ACP 165.00 1060 12.00 12.10 11.50 0.98 2.08
    5.56 x 45 62.00 3100 6.43 9.58 5.57 0.41 2.29
    7.62 x 39 123.00 2400 8.60 11.35 7.92 0.55 3.51
    7.62 x 51 150.00 2800 8.77 11.94 7.82 0.51 5.00
    7.62 x 54R 174.00 2610 8.53 12.37 7.92 0.45 5.41
    .50 BMG 647.00 3044 14.20 20.40 12.95 0.46 23.45
    .223 Rem 77.00 2750 6.40 9.60 5.70 0.41 2.52
    7.62 x 25 85.00 1230 9.40 9.70 7.80 0.93 1.24

    Calculating bolt back travel requirement:
    -------------------------------------------------
    Bolt back travel requirement X = (2*Ke/Ks) ^0.5
    Ke = 0.5 * Bolt-weight * Sv ^2
    Ks = spring constant (i.e. 30lbs/in or 360 lbs/ft)
    Example:
    For 9mm Nato
    Ke = 0.5 * 1.78 * 6^2 = 32.04
    X = (2*32.04/360) ^0.5 = 0.4219 (ft) or 5.06 in

    Sv and bolt weight are interrelated, so using an un-correlated bolt weight would produce incorrect result. Change Sv and recalculate the bolt weight to get the desired weight first.

    Note that for maximum/safe push back, the spring has very little effect.


    Shooter

  5. #15
    Gunco Regular Shooter17's Avatar
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    The goal is a modern version with better trigger
    If you want to retain the original exterior appearance, Trickyrick did a superb job using a modified AR FCG that was located forward in the Sten trigger housing that used the Sten trigger/linkage to actuate.
    If you dont care about the original appearance, there are lots of options.
    An AR FCG, a G3 FCG and housing, Rem 870 trigger group are just a that have been used.

    Shooter

  6. #16
    Gunco Member grumpy7mag's Avatar
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    thanks for the math. I have been so deep in reloading it was missed. So how to guess spring pressure or did you say that it doesnt matter?

  7. #17
    Gunco Member grumpy7mag's Avatar
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    Does anybody have other templates to share so we all can have a complete set???

  8. #18
    GuncoHolic twa2471's Avatar
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    Man I'm glad you guys put this info up. I'd been considering one of the Stens but hadn't found info for them before.

    NOW,,, to see if any kits are still left! To bad I'll have to farm out the machine work if I can find one, drat!

  9. #19
    Gunco Member Korn's Avatar
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    I bought a MK3 kit from Apex a few weeks ago.

  10. #20
    GuncoHolic twa2471's Avatar
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    That's where I was looking also. How do they look and are they anywhere near maching# ? That can sure save allot of time when they do match, everything already works together right.

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