M72 in .308?
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Thread: M72 in .308?

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    Gunco Member pmr1010's Avatar
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    Default M72 in .308?

    I have an M72 parts kit with a virgin barrel, the correct one, heavy with cooling fins. Since I have no receiver as of yet, I wondered how difficult it would be to convert it from 7.62x39 to 7.62x51? The bore is the same if I'm not mistaken, and 12mm could be made up with gentle movement. The barrel could handle the heavier pressure of the .308 round.

    Please advise on this. I have read several other chamber change threads and have read that the .308 bolt has larger locking lugs. So would the lower rails have to be mounted lower? Having not seen a Kalashnikov chambered for this round I am unfamiliar.

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    No Hope For Me 1biggun's Avatar
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    I have an M72 parts kit with a virgin barrel, the correct one, heavy with cooling fins. Since I have no receiver as of yet, I wondered how difficult it would be to convert it from 7.62x39 to 7.62x51? The bore is the same if I'm not mistaken, and 12mm could be made up with gentle movement. The barrel could handle the heavier pressure of the .308 round.

    Please advise on this. I have read several other chamber change threads and have read that the .308 bolt has larger locking lugs. So would the lower rails have to be mounted lower? Having not seen a Kalashnikov chambered for this round I am unfamiliar.
    SEE MY 308 CONVERSION THREAD ITS A LONG READ BUT ITS FULL OF VERY GGO INFO THE BEST YOU WILL FIND ON THE NET READ AND UNDERSTAND ALL OF IT THEN DECIDE IF YOU WANT TO TAKE THE RISK. THE RAILS DONT NEED TO BE LOWER. YOU NEED TO READ THE THREAD FIRST ILL FIND THE LINK FOR YOU

    IT NEEDS TO BE A DAMMM STICKY !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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    No Hope For Me 1biggun's Avatar
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    ffff
    Last edited by 1biggun; 05-21-2016 at 08:18 PM.

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    Gunco Member pmr1010's Avatar
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    Thank you for that link and all of the research and work that you did already! I had begun to read that thread earlier, very informative.
    This is an additional question in relation to what you wrote above about pressure and what I read in yours and other threads. I am not new nor am I experienced at all factors regarding this topic. But something that always made me curious is the pressures of some cartridges being higher than others. 30-06 is higher than 8mm, which is roughly that of the 7.62x54r which is lower than a 7.62x39. Is it the type of powder? This might seem silly to some, but the varying size shells not necessarily having pressures with any correlation to each other is confusing.

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    Happy Camper hcpookie's Avatar
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    Welcome to the wonderful world of ballistics

    Yes powder selections can play a HUGE part - which is why there are so many specifications in the reloading manuals. When you start asking those questions, you are getting into the fundamental cartridge design characteristics as well. It is hard to compare any particular cartridge to one another because the designs are all different. Apples to oranges.

    I am personally convinced the AK design will power all but the most powerful of cartridges without modification. The locking lugs were bigger only on the Yugo AK designed .308 bolt, but on others the lugs are the same size. I can't remember how the Galil or Valmet .308 bolt looks... memory fuzzy on that design.

    According to a discussion a friend had with some of the guys AT the Izzy factory, the 3rd lug on the .308 was there to provide better accuracy, not for more strength. I never followed up with him to verify this.

    My .308 conversion works great, although I screwed up and drilled the gas hole WAY too big, so I have to vent more gas than I would like. If I did not vent the gas, the operating forces were way too high. Meaning more recoil and shorter life of the parts. Of course venting more gas = wasted gunpowder, however I don't plan to use it for long-range shooting.

    http://www.gunco.net/forums/f244/sco...e-clone-35244/

    http://www.gunco.net/forums/f244/308...-update-32208/
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    Gunco Member pmr1010's Avatar
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    Nice stuff Pookie.
    As far as the barrel, the M72 heavy barrel can handle it, Zastava still makes the .308 version and by the specs on their site it looks like the receiver and barrel are the same from 39mm and 51mm cartridges.

    Also, from what I've read, it looks like the front trunnion is machined more to accommodate the longer round.

    My only real confusion at this point is the bullet diameter. I've read the difference between .311 and .308 is the issue. Maybe I read the posts wrong. My confusion is that I thought the 2 rounds were in metric 7.62x39 and 7.62x51. 7.62mm is 7.62mm no matter how you slice it. Is this mainly dealing with .308 Winchester rounds as opposed to NATO rounds?

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    Gunco Maniac sjohnson's Avatar
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    Since rifling is present, you must consider the bore and the groove diameters.

    7.62 is the bore, .30 inches. The depth of the grooves dictates the bullet size. With a bore of .30, the 7.62x39 has a nominal groove diameter of .311 while the 7.62x51 has a nominal groove diameter of .308. Hence the bullet differences.
    I have a daughter. I tell her, "911 is what you dial after you're raped. 1911 is what you should have before they try."

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    Gunco Member pmr1010's Avatar
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    Aha! Well that explains a lot. That was what I was misunderstanding.

    So then, back to reading more.

    I didn't see that explanation or at least didn't pick up on it. I'll have to read slower. In my enthusiasm I'm reading too quickly. I'm trying to read as much as possible to figure it out on my own but sometimes it's the little things that get away from me.

    Thanks again.

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    Since the kit has the finned .311 barrel, the logical choice is 7.65x53 Argentine Mauser. Just a bit longer than a .308, less pressure, fits M14 and G3 .308 magazines, probably others too; those are what I had on hand to check with.

    You have to buy bulk brass from Graf or cut down .30-06 brass, but you use the same .311 bullet as the 7.62x54R or .303 British.

    Reamerrentals.com has the 7.65 reamer for rent, if I remember right.


    If you just want to blaze through a few boxes of ammo and leave the empties for someone to pick up, you probably won't want to shoot 7.65. Otherwise, it costs the same as reloading for 54R.

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    No Hope For Me 1biggun's Avatar
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    ffff
    Last edited by 1biggun; 05-21-2016 at 08:18 PM.

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