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Thread: Barrel Blanks

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    Happy Camper hcpookie's Avatar
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    Default Barrel Blanks

    Droog's quest for a long-barrel AK got me thinking.

    His pic:
    http://www.gunco.net/forums/attachme...achmentid=5141

    ... inspired me to further research AK barrel blanks. By "AK Barrel Blank" I mean a barrel that is "full diameter" and is capable of conversion into any standard barrel configuration.

    Here's what I've dug up... in short, .303 British barrels can be converted for use as an AK barrel, in all flavors that use standard .311 bullets.

    NOTE: A prime application could be replacements for Yugo M70 "shot out" barrels!

    Specs:
    .303 British specifications:
    bullet diameter .311-.312",
    maximum COL 3.075",
    maximum case length 2.222",
    SAAMI MAP 45,000 cup.
    Twist: 1 in 10"

    7.62x54R specifications:
    bullet diameter .308" or .312" (depending on rifle),
    maximum COL 3.048",
    maximum case length 2.115".
    Twist: 1 in 9.5" RH

    7.62x39 specifications:
    bullet diameter .311",
    maximum COL 2.20",
    maximum case length 1.528",
    MAP 50,000 cup.
    Twist: 1 in 10"

    .308 caliber is too small for use in a .311 barrel. Of interest, "standard" .30 caliber cartridges are the same diameter- .30-06 is a .308 diameter. Therefore, a heavy-duty .308 barrel could be adapted from 1919 .30-06 barrels... food for thought.

    Normally we're talking about 7.62x39 and that is what I'll limit this to for now.

    The 7.62x39 cartridge dimensions are slightly smaller than a .303 Brit cartridge. This means that a .303 Brit chamber can be converted to 7.62x39 by trimming the breech just under .7" to make up the difference. Once an extractor notch is cut, the barrel journal sections could be spun on a lathe. The cartridge specs make it appear that the chamber would not need to be reamed (or for that matter, sleeved) to work with the 7.62x39 cartridge.

    There is an "Enfield K" project out there that converts Enfield barrels to 7.62x39 for a bolt-action conversion. Enfield Mk 4 barrels are reportedly "thick enough" for use with AK barrel attachments. Due to the "loose fit" of the smaller 7.62x39 cartridge, a "shot out" barrel with enough throat erosion could cause tumbling of the 7.62x39 bullet, therefore requiring chamber reaming to compensate for the wear. Worn riflings would not be fixable.

    Here is the link to the "Enfield K" project:

    http://www.specialinterestarms.com/#Enfield%20K


    Northridge sells Enfield Mk4 barrels for $50 or so. I think these are 27" but am not sure.

    Bren barrels are 25" long but have a gas port cut into them. I do not know the location, but I will assume they are not in the proper location for an AK gas port. I am not certain how easy it would be to plug-weld or "pin" this hole closed. I have inserted a threaded pin to close off a 45-degree hole on my AK-103 project, so I know it can be done. The uncertainty is that I am not sure how the threaded plug could be secured in a Bren barrel. I have been told from some "in the know" welder folks that MIG/TIG welding will induce enough heat to kink the barrel. I have also been told by "other" welder folks that this is negligible and can be safely welded. This may or may not affect accuracy, and I have no data to confirm/deny this. IF this is acceptable, this is a prime source for replacement RPK barrels!



    Now about 7.62x54R:

    ROMAK and Dragunov (and PKM) barrels: The 7.62x54R cartridge is slightly larger diameter which means a chamber reamer would be necessary, but the bullet would work in a .303 barrel. Since there are enough Mosin-Nagant (and Mauser) barrels out there, this may represent a barrel resource that could allow us to build Dragunov-style rifles. Since the ROMAK-3 is for all practical purposes a long-barrel AK, this has obvious applications with using only a standard AK kit.

    PKM barrels would most certainly need to be as thick as an RPK build in order to ensure a safety margin, and Bren barrels could probably be fit to this purpose. I don't have a PKM kit - yet - but I'd like to have a spare barrel for it.



    Safety concerns should be negligible, since the chamber pressures are comparable. Safety of a 50+ year old barrel may be a concern due to metal fatigue, but I am not certain if this can be measured or quantified in any way. It may be of no consequence at all.


    In summary, Enfield and Bren barrels share enough dimensions that they could physically be converted to use the AK cartridge. A lathe is required, a mill is a good idea. A chamber reamer is required for 7.62x54R caliber.

    I'm open to all comments about recycling 303 barrels in this manner...
    Last edited by hcpookie; 07-05-2005 at 09:37 PM. Reason: Added link for Enfield conversion

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    Friend of MCMXI Preacher's Avatar
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    An AK with a 27" barrel??

    You sir have my undivided attention!!!
    You only have the rights you are willing to fight for.
    I Like 1911's.

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    GuncoHolic scubadvr's Avatar
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    If we could get the bolts one in 223 would be hot shit!!! Stainless steel, National Match, now I know I'm dreaming.
    Be sure to check out:
    www.warroom.com
    and
    www.michaelsavage.com


    ******************************************
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    BANNED jpglee1's Avatar
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    What ejector notch?? Im confused, why would you need to put an ejector notch into an AK BBL???

    Heh...I think you need to go to Darra, Pakistan for a few weeks... they'd set you up right w/AK knowledge!!!

    http://www.madinpursuit.com/pakistan/paki_13b.htm

    http://www.khyber.org/pashtoplaces/darraadamkhel.shtml

    My wife and I are going to Pakistan in a year I hope... Darra is on the top of the to-do list...

    Ahh... charas and AK's... that's the life





    you gotta figure out what Charas is

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    Happy Camper hcpookie's Avatar
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    I would like to find a source for 5.45 barrels, and this whole barrel ban nonsense would evaporate in my mind. That's .21457" for those that care. Since it is smaller than 22LR, the only places I would guess to look are those that make 17HMR barrels.

    There *IS* a 5.45x39 US-built barrel, by AlexanderArms.Com. They have "re-packaged" the caliber into the ".21 Genghis" for the AR platform.

    http://www.alexanderarms.com/website/id9.html

    No word on how much the barrels run... that's a bad sign!

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    Happy Camper hcpookie's Avatar
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    Quote Originally Posted by jpglee1
    What ejector notch?? Im confused, why would you need to put an ejector notch into an AK BBL???
    The extractor on an AK sticks out farther forward (closer to the barrel) than the face of the bolt.

    The "extractor notch" or more precisely, the "extractor groove" is that recessed section that allows the extractor to clear, thereby allowing the bolt face to seat more closely against the breech. This prevents excessive bulging of the base of the cartridge.
    Last edited by hcpookie; 07-05-2005 at 07:17 PM. Reason: "extractor" not "ejector"

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    BANNED jpglee1's Avatar
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    Oh...I guess I just didnt pay attention that close.. I always thought the ejector was the part on the receiver LOL...

    you're talking about the EXTRACTOR.... not trying to correct you, thats why it was confusing me...the ejector is the little doohickey on the left rail...


    L8R


    P.S. 2pts if you figure out what charas is

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    Happy Camper hcpookie's Avatar
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    (Slaps forehead) yes you are correct. The extractor... been a long day! Edited for correction.

    Wanted to add this wonderful tech data I found RE: cartridge sizes:

    http://7.62x54r.net/MosinID/MosinCartridges.htm

    (Droog, you see this?) this could be used to build a chamber reamer if you don't want to buy one. I've read on other BIY forums that home gunsmiths usually build their own reamer vs. buying one... haven't searched Brownell's so I really don't know how expensive they are...

    Edited to add - discussion on the home gunsmith forums indicate chambers should run loose (larger) up to .005", therefore chamber reamers should be made with .005" larger diameter than those listed. I would have to measure a known chamber size vs. the specs to verify this.
    Last edited by hcpookie; 07-08-2005 at 09:07 AM.

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    BANNED jpglee1's Avatar
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    OK buddy... hi-jack mode OFF LOL


    L8R

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    Chief Administrator 7.62x39's Avatar
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    Pook,

    You never cease to amaze me with the cool stuff you come up with.

    Thanks
    .

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