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  1. #1
    Join Date
    Mar 2011
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    6,127

    Default 7.62X39 to .308 Adapter Worries?

    I just bought a neat little chamber adapter that lets me shoot 7.62X39 in a .308 by basically filling the chamber with a .308 cartridge-sized hollow adapter that holds a Russian cartridge inside it. (I use such an adapter to shoot .45 LC in my Martini-Henry "Zulu" rifle, a cheap solution to very expensive and rare ammo.)
    The Russian bullet in the .308 adapter travels a short distance unrestricted through a smooth and loose section of the adapter before entering the throat's rifling. .
    Joop brought up an interesting and very relevant thought on such an adapter -that it might possibly lead to damage to the throat of the rifle using the adapter.
    I've been wondering if this might happen. It seems it is possible for two reasons, but I'm not sure whether it would really be a problem:
    1) Hot gases might leak past the bullet base as it is fired and going through the loose straight section, burning the throat more than they would do if behind the bullet. Are hot gases more destructive to the throat in this situation than if they hit a microsecond later behind the bullet normally? Doesn't seem like it, but maybe.
    2) The bullet might enter the throat angled or off center a bit from free travel before hitting the throat, resulting in uneven pressure and wear. In this scenario the FMJ bullet from the Russian round is slightly skewed and sort or rattles into the throat, seemingly very possible.

    The second scenario seems more likely to damage things than the first to me, but it is perhaps no more dangerous to the barrel than using shorter bullets in the regular .308 chambering that don't reach all the way to the throat, like soft-points. It used to be that for maximum accuracy it was believed a bullet had to be pushed right up against the throat, but I think that belief may have been discarded, meaning lots of bullets come rattling up to the throat a bit loose.

    As I very much value Joop's wondering about the possibility of barrel erosaion or wear and don't know an answer, any thoughts from other members? I haven't tried the adapter yet.

    .

  2. #2
    Join Date
    Aug 2011
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    The Texas Blackland Prarie between the Elm Fork and the East Fork of the Trinity River.
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    962

    Default

    I bought a handful of cartridge conversions from a company called Ptarmigan. I've never tried them. Unless you have at least a half dozen, it is such a slow process...it would seem.

  3. #3
    Join Date
    Jan 2010
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    855

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    On top of your concerns 7.62x39 is usually loaded with a .310 diameter bullet and you are tring to force it through your 308 bore. I don't think I would do that.

  4. #4
    Join Date
    Jan 2009
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    4,231

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    Quote Originally Posted by groovy mike View Post
    On top of your concerns 7.62x39 is usually loaded with a .310 diameter bullet and you are tring to force it through your 308 bore. I don't think I would do that.
    This was my biggest concern. To add to that, most commercial 7.62x39 ammo has a bi-metal jacket (steel) that will likely only expedite the problem (not as big of an issue as most US rifle snobs would like people to think, but when you start pushing it through a bore that's smaller than what it was designed for, I can see it being a possible factor).

    John

    ETA: I forgot to ask; Do you handload? You could use 110 grain .308 bullets with a mild charge or, if you're loading for Mosins, use the smaller 124 grain projectiles made for x39, using the same theory. And, if you load them hotter, they're super fast and accurate, as well.

  5. #5
    Join Date
    Apr 2009
    Location
    Ohio
    Posts
    879

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    Quote Originally Posted by groovy mike View Post
    On top of your concerns 7.62x39 is usually loaded with a .310 diameter bullet and you are tring to force it through your 308 bore. I don't think I would do that.
    2 thousandths of an inch is nothing to sweat over. Most people don't realize how small that is, it's probably within the tolerance of the barrel diameter for most surplus military rifles.

  6. #6
    Join Date
    Jan 2010
    Posts
    855

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    Quote Originally Posted by izzytok46 View Post
    2 thousandths of an inch is nothing to sweat over. Most people don't realize how small that is, it's probably within the tolerance of the barrel diameter for most surplus military rifles.
    agreed but we dont know if it is being used in a military rifle. and just because it is "probably" all right doesn't mean its a good idea!

  7. #7
    Join Date
    Dec 1969
    Posts
    806

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    I bought one from a guy in Alaska, I installed it in a Spanish 1916 rifle in 308 and only shot 100 rounds thru it and didn"t have any issues with it. I liked it.

  8. #8
    Join Date
    Mar 2011
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    That's who I bought from - I don't handload currently, but may have to take it up again.

    Quote Originally Posted by bsd View Post
    I bought one from a guy in Alaska, I installed it in a Spanish 1916 rifle in 308 and only shot 100 rounds thru it and didn"t have any issues with it. I liked it.

  9. #9
    Join Date
    Dec 1969
    Posts
    6,991

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    Is that guy still in business or did you get the adapter sometime ago? I could use one of those 7.62x39 adapters for my Spanish 1916.
    Damn the expense, use your turn signals today... and as a special favour, try doing it before you have two wheels in the next lane.

  10. #10
    Join Date
    Mar 2011
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    I just got it. Quick delivery. The adapter is temporarily glued into the chamber with Loc-Tite.
    Here's his link:

    http://www.mcace.com/adapters.htm

  11. #11
    Join Date
    Dec 1969
    Posts
    6,991

    Default

    AHA! Good news. I emailed them ages ago and got no reply so I thought they had gone under even though the site is still up.
    Damn the expense, use your turn signals today... and as a special favour, try doing it before you have two wheels in the next lane.

  12. #12
    Join Date
    Dec 1969
    Location
    Congo, DR
    Posts
    1,134

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    I wouldn't give it a second thought when "downsizing' with adapters. Check your bolt face for obvious signs of blow by, but I don't thin you'll have any problem.

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