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Thread: 7.62 bolt head to 5.56

  1. #11
    Happy Camper hcpookie's Avatar
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    So when are we going to get serious about US-build bolts? We have them for AR builds... just thinking aloud. That rotating lug is the only thing on a bolt that has me puzzled. The rest is just lathe and mill work. And of course heat treating.

  2. #12
    Gunco Veteran muttman's Avatar
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    if I ever get some me time with autocad at work. muttman

  3. #13
    Gunco Member FordGalaxy's Avatar
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    Rotating Lug ??? now I'm confused I thought the whole bolt on an AK rotated.

    The AR has rotating lugs but they're just cammed by the carrier like an AK.

    Home made bolts, I like it, and the front trunions would not be to difficult to make either, bullet guide looks to be more work.

  4. #14
    Gunco Member jimmy_stikx's Avatar
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    Honestly, it looks like they used an end mill, and milled the meat from around the carrier lug one pass, and partial rotation at a time.

    But then, I'm not that well versed with mills or machining.

  5. #15
    No Hope For Me 1biggun's Avatar
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    as far as it just being a 223. the 223 has over 50,000 psi or about 54,000-56,000 CUP. and even though the rim is smaller and it will reduce the bolt thrust some it does not reduce it a lot (some were here there is a formula for figuring it out.) If I remember right the bolt thrust was higher than the 7.62 x 39.
    I tig weld and all other types as well and passed a certifed welding test 20+ years ago before I actually welded very well at all it is not that hard (No I do consider myself certifed or am I currently certifed). I also have some back ground in metalogly and failure analsis. for any thing to be welded the parent metal has to become molten and that is going to change the structure of the metal that area can act as a stress riser and a crack can devlope. even if a heat sink is used you still have to get the area hot enough to melt were the welding is being done. that spot is going to be different than the rest of the bolt. if it will fail I have no for sure way to say yes or no ( it likely will not) but I do feel it is more prone to fail after a part of it has heated up and had the temper changed . yea the Kvar bolts are a little pricey but I orderd 3 at a time and the bulgy5.56 mags and the 5.56 bullet gude and all the extra pins and crap that I think I will need so the shipping is not a big deal. and again you also need to have a spring loaded firing pin if you plan on shooting comercial ammo so figre all that in as well. as stated above dont do it if your not comfortable so again this is why I dont do it. sorry for the typeos It is late and I just got done loading 500+ round of 223 on a single stage press and Im tired.

  6. #16
    Gunco Member FordGalaxy's Avatar
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    500 rounds on a single stage ouch, I Love my projecter. Used to load target ammo on a single. But I dont shoot for money anymore. Can't see the front sight on my handguns without my readen specs anyway. Thinking about some of those colored fiber optic sights.

  7. #17
    No Hope For Me 1biggun's Avatar
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    I will defenatly looking for at least a turret press in the near future. I am pretty new to the reloading game but so far it is working out.

  8. #18
    Gunco Veteran muttman's Avatar
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    Quote Originally Posted by 1biggun
    as far as it just being a 223. the 223 has over 50,000 psi or about 54,000-56,000 CUP. and even though the rim is smaller and it will reduce the bolt thrust some it does not reduce it a lot (some were here there is a formula for figuring it out.) If I remember right the bolt thrust was higher than the 7.62 x 39.
    I tig weld and all other types as well and passed a certifed welding test 20+ years ago before I actually welded very well at all it is not that hard (No I do consider myself certifed or am I currently certifed). I also have some back ground in metalogly and failure analsis. for any thing to be welded the parent metal has to become molten and that is going to change the structure of the metal that area can act as a stress riser and a crack can devlope. even if a heat sink is used you still have to get the area hot enough to melt were the welding is being done. that spot is going to be different than the rest of the bolt. if it will fail I have no for sure way to say yes or no ( it likely will not) but I do feel it is more prone to fail after a part of it has heated up and had the temper changed . yea the Kvar bolts are a little pricey but I orderd 3 at a time and the bulgy5.56 mags and the 5.56 bullet gude and all the extra pins and crap that I think I will need so the shipping is not a big deal. and again you also need to have a spring loaded firing pin if you plan on shooting comercial ammo so figre all that in as well. as stated above dont do it if your not comfortable so again this is why I dont do it. sorry for the typeos It is late and I just got done loading 500+ round of 223 on a single stage press and Im tired.
    1biggun,
    I agree with your statment "if you dont feel" that is the point of the home brew type gun, and shipping is not that bad, for now. I personaly dont think a bolt that has a "ring" with a press fit then tig welded on the outer most part of the bolt head will change the temper of the luges. all three of the metalolgist at work, one of witch has a back ground in welding state that welding will change the temper but not to the point of failure. I'm not saying there word is 100% but it is the best ed. guess that I can come up with at this point in time. I welcome what you wright in this form. at this point in time a .223 ak is about progect #3 on the to do list, not in cluding the honey do list that will not stop growing on a daily rate. so I have some time to ponder on this one. as far as the spring loaded firing pin I think hcpookie has worked that one out on his .308 build.
    btw have you given anny thought of using a -74 mag with a modifide follower for your .223 ak. -74 mages are cheeper and the mod. is easy to do. muttman

  9. #19
    Gunco Member FordGalaxy's Avatar
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    If you clamped a couple of copper heat sinks to the bolt I don't think the lugs would get hot enough to lose any of their temper . A few small quick tack welds is all that it would take and let it compleatly cool between welds. Silver solder should also work, solder the ring first then cut the clearance for the extracter. The base of a case is designed to take the pressure of a round. Its only when folks try to get more out a round than it was designed for or there was a mistake made that they fail. Guns that head space on the shoulder or case mouth do not always compleatly enclose a round. The 1911 is the worst culprit that comes to mind. The barrel and web in the case head are what contain the pressure. Metal used in guns is usually not all that hard, and if a part is hard it is usually more for wear resistance, and improve resistance to perminant deformation. Metal selection and heat treat is not so much about containing the pressure as it is the 10,000 times the bolt will be slammed into the lugs. Which is why excessive head spacing is bad, it gives the bolt a little room to gain some speed before it slamms the lugs.

    Now I'm not a metalrgist, I'm an electrician, but I did learn a few things about metal when I was a job shop machinest, and some cool stuff about heat treating and tool steel when I was making chips in a tool and die shop.

    So don't try this at home folks and I am in no way recomending anyone else try it,

    when I get to the .223 project after the milled rewelds and the tabuk I'm going to tack weld a ring into a romy bolt.

    hey muttman got a link for that 74 mag mod?

  10. #20
    No Hope For Me 1biggun's Avatar
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    I would be interested in the mag mod. I am only using 10 rounders in my build as it is shot from the prone position 99% of the time. the bulgy mag was cheap enough and I only need 2. I have also seen some galil mags in shot gunnews that were priced fairly reasonably. I have seen HC,s firing pin conversion and plan on doing some thing simular on both my 308 build and a 1.5x308 build. I have been reloading using the military type hardend primers, so for now I have gotten away with out spring loaded pins on the 7.62x39 builds.

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