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Thread: 308 ak

  1. #251
    Gunco Regular smartbomb's Avatar
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    1biggun, would a psl be a better platform to do a larger cal conversion. i ask only because i saw a psl receiver with trunnions really cheap. got me wondering after reading this thread if this would be a better alternative. i found somewhere the x54 chamber pressures are in the upper 50k psi range. kind of makes it consistent with the 308.

    given i have recently gotten into building my knowledge base in comparatively small compared to many here.

    man a 338 lapua or 7mm mag would be wicked shoot.
    al gore is full of carbon enriched shit

  2. #252
    No Hope For Me 1biggun's Avatar
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    it can be done likely on a psl how ever you will still need to lengthen the mag well as well as also deal with a much larger bolt face. It all depends on what x54 ammo your looking at some is really hot. If you can get a reciver and trunion cheap go for it you will still need a carrer and bolt. it may be possable to mod a standard bolt and trunion to work. Im not really sure if there are any real streangth gains over say a m70.

    IMOO a ak 74 bolt on a Yugo trunuion should give the most streangth possable with standard AK parts. that are not super hard to find. Im thinking a AK 74 trunion would possably in second place.


    If I had no parts lying here Id buy a bulgy ALK 74 kit as a doner kit and go from there. I have yet to see any documented cases of a trunion failure in any calibur or conversion. it seems the bolt would be the weak link. untill some one actualy has a failure its hard to say.

    My 243 build is back on the bench and I hope to unt with it next month. after that I plan on some hot load testing and care full measure ments of head space changes.

  3. #253
    Gunco Regular smartbomb's Avatar
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    for those who despise math, i took the gwbasic bolt thrust/sheer program and did a re-write in c++ as an .exe to run standalone. once i get it tweaked i will port to javascript an make it as a webpage. so far so good.
    al gore is full of carbon enriched shit

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  5. #254
    No Hope For Me 1biggun's Avatar
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    xxx
    Last edited by 1biggun; 03-06-2016 at 11:57 PM.

  6. #255
    Gunco Regular smartbomb's Avatar
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    biggun sorry about the trip down geek lane. question 1, do you want to calc just the thrust. this is easy given there are only 2 defined variables, case head diameter and chamber pressure. the original code i was working with was a bit more complex in the sense that it requires you to provide more info (some that may be difficult to obtain) such as # bolt lugs (easy), width of one lug (not as easy), diameter of bolt lug (not so easy). the payoff is getting calcs for lug strength lug shear and lug flex.

    given the formula info from lilja barrels, it was somewhat easy to write an app to handle the calcs.
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    al gore is full of carbon enriched shit

  7. #256
    No Hope For Me 1biggun's Avatar
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    xxx
    Last edited by 1biggun; 03-06-2016 at 11:57 PM.

  8. #257
    Gunco Regular smartbomb's Avatar
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    i can handle the math and the program as long as its simple. like you said there are so many variables that cannot be accounted for. at this point you almost have to make assumptions based on what ever info is available. it really difficult to predict to the gnats-ass whats really happening. the best way to handle the data is take a safe approach and build in a fudge factor based on the assumptions. the idea is to get a reasonable prediction of what the forces will be. i used the formula supplied on dan lilja's web site. after looking at his calculations there are some questions i have asked regarding some of the numbers used in his formula.

    now something simple like thrust is straight forward enough to do. adding flex and lug shear make things a tad more difficult. if you have some particular data caliber, case head diameter, chamber pressure) you want to see send it to me. i will try to get you a chart showing the thrust.

    i am a complete noob with gun building, even tho i have been around them all my life. i have just started this as a new hobby and have a shitload to learn.

    cheers
    scott
    al gore is full of carbon enriched shit

  9. #258
    Gunco Veteran jreifsch80's Avatar
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    How about pooling together and investing in some cheap romy trunnions and bolts and doing some real world proof testing I'm sure a bolt and trunnion could be bought for about 40 bucks I'd buy a set for the cause. I think we could step up the loading on say a .308 untill we have failure see how a couple sets compare and it gives us some good real world results which I think would be well worth the pooled cost, biggun, let me know if you're interested in doing a real proof test and I'll send you a spare romy trunnion and bolt.

  10. #259
    No Hope For Me 1biggun's Avatar
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    xxx
    Last edited by 1biggun; 03-06-2016 at 11:58 PM.

  11. #260
    Gunco Veteran jreifsch80's Avatar
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    Hmm you bring up some interesting thoughts, I was thinking the same as you that there's no need for a full gun in fact just a trunnion barrel bolt carrier fcg and like a tapco flat.

    I was thinking maybe a .243 might be better for tested and if possible load in steps all the way to 125% unless of course we have failure before, you're right as we could test with x39 but while we could get some high pressure I think it would be easier to get very high bolt thrust levels without worrying as much about case failure..

    I like your yugo barrel idea as it would kill 2 birds with one stone like you said. Also if the thin yugo barrel romy trunnion and bolt are able to fair well with some serious proof loads then I think it would give more confidence in caliber conversions. The math is great but some things just need to also be proven in real tests as well. I also might be able to dig out a yugo bolt and trunnion for testing as well

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