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Thread: CETME-47 (CETME in 7.62x39)

  1. #1
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    CETME-47 (CETME in 7.62x39)

    I have been giving it some thought and instead of building my CETME kit in .308, I am going to put together a CETME in 7.62x39. From what I have been reading online the two big challenges to this are the barrel/ chamber and the locking piece. For the barrel, I plan on getting a PTR-32 barrel off of HK parts that already has the correct fluting in the chamber. For the Locking piece I plan on using a #15 RCM LP for an HK, with a new HK bolt head. (Yes I know that the general consensus it that Bolt heads and Locking Pieces cannot be swapped between a CETME and HK carrier. However, I have never seen a great explanation as to why other than “they are different sizes”. See my post here for my details on my train of thought. http://www.militaryfirearm.com/Forum...-CETME-Carrier) Ideally, I would like to make it run on standard AK magazines so I will also be designing an insert for the mag well.

    Right now I am just working on sourcing parts and making sure I get my 922r compliance in check.

    Proposed Parts List

    Base Part Kit- CETME C from Apex
    Barrel- 16” for a PTR-32
    Receiver- CETME C flat
    Trunnion- CETME C from Parts Kit.
    Muzzle attachment- US made might go for a standard cage might get something a little more exotic. Only time will tell.
    FGC- Modified/ simplified CETME Pack (Trigger and Sear welded together)
    Bolt Head and Locking Piece- New US made HK parts.
    Bolt Carrier- CETME C from parts kits
    Pistol grip- 3d Printed my design
    Stock and handguard- Custom made by me. I am currently working on making my own metal handguard fittings and will probably post a thread when I have the technique down pat.
    Cocking Handle- From parts kit
    I am also just assuming that all of the magazines parts will be foreign.

    That puts me at 7 US parts and 9 foreign parts. I might even add in a US made cocking handle if I come across one.

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    holescreek's Avatar
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    FGC- Modified/ simplified CETME Pack (Trigger and Sear welded together)
    I believe you meant to say that you're welding the trigger to the disconnector. You won't be using the sear.

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    WildBillCody's Avatar
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    That should be cool, I'm pretty sure I've seen it done before, I think I saw one that was made to look like a STG-44, that would be cool...
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  4. #4
    holescreek's Avatar
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    I dug around a little bit for my original thread on building a Cetme in X39 back in Feb of 2010 to see if there was any useful info (not much). I was able to fix a few of the old fubared photobucket pics but don't have all of them available at the moment.
    http://www.militaryfirearm.com/Forum...consider/page3

    To put it into context, in those days the PTR32 did not exist but was being talked about in the building community. There wasn't a gun available to pattern a build after and I was just figuring out how to do chamber fluting at home . A couple weeks later, the first gen PTR32 was rolled out but was pretty rare - even back then. This all took place before the locking piece and trunnion studies and it was only my 3rd Cetme build.

    The only thing that may or may not come into play for you is the extractor mod I did (not sure how necessary it really was now). I played with shortening the recoil spring so the cartridge would eject but in retrospect that was the wrong place to start. If memory serves I ended up with a slightly shorter recoil spring and a reduced strength bolt locking lever spring. Those mods may or may not be necessary for you since you're using the correct locking piece to start with.

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    Quote Originally Posted by holescreek View Post
    I believe you meant to say that you're welding the trigger to the disconnector. You won't be using the sear.
    Yes that is correct.

    Quote Originally Posted by holescreek View Post
    I dug around a little bit for my original thread on building a Cetme in X39 back in Feb of 2010 to see if there was any useful info (not much). I was able to fix a few of the old fubared photobucket pics but don't have all of them available at the moment.
    http://www.militaryfirearm.com/Forum...consider/page3

    To put it into context, in those days the PTR32 did not exist but was being talked about in the building community. There wasn't a gun available to pattern a build after and I was just figuring out how to do chamber fluting at home . A couple weeks later, the first gen PTR32 was rolled out but was pretty rare - even back then. This all took place before the locking piece and trunnion studies and it was only my 3rd Cetme build.

    The only thing that may or may not come into play for you is the extractor mod I did (not sure how necessary it really was now). I played with shortening the recoil spring so the cartridge would eject but in retrospect that was the wrong place to start. If memory serves I ended up with a slightly shorter recoil spring and a reduced strength bolt locking lever spring. Those mods may or may not be necessary for you since you're using the correct locking piece to start with.
    Thank you for digging out those old photos, I had stumbled on that thread a while back and as the saying goes, a picture is worth a thousand words. I was wondering what exactly was done to the extractor on your build. I think if I do have to go down that road I will try and pick up a PTR-32 replacement part. I don't know if it will fit in a standard Bolt Head but something in my gut tells me it is easier and cheaper to redesign a extractor than it is a bolt head.

  6. #6
    holescreek's Avatar
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    Since these guns are blowback operation the only function of the extractor is to hold the cartridge brass against the bolt head long enough for the ejector to kick it out of the receiver. As long as there is enough "grab" on the brass there shouldn't be any need to modify the extractor. The well worn Cetme model B bolt head I used for mine was a bit too sloppy for my taste and it was necessary to move the extractor in just enough to hold the brass tight. I've wondered if the PTR32's used a different bolt head than the 91 but never looked into it.

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    Quick update, RTG Parts order came in today and I now have everything, with the exception of a few odds and ends and tools, to get going. I spent the last few weeks working on the buttstock and Handguard. I picked up a nice piece of spalted maple that hopefully will look good when done. After that I will move on to the trigger assembly, receiver, barrel, AK mag holder and then final fitment.

    I have already found a few points of contention when doing a quick dry fit up, I am sure I will find more as time goes on.

    1. The area of the PTR barrel where the triple frame sits measures .711" in diameter. The CETME triple frame is .651". I plan on reaming the triple frame out with a 45/64 ream which is .7031". I think that will still give a good interference fit but not be too small. I did not find anything pointing to what size ream was being used for the PTR barrels.

    1B. The other issue is by reaming the triple frame out I will lose the cool grenade launcher holder rings in the front. Function wise, no big deal; cool factor wise, it sucks. To hopefully get around that I am going to fill the two grooves with a shallow weld and file them smooth. That will hopefully keep the cool-ness without being too much work since I don't own a lathe.

    2. Cocking tube is slightly bent. I will be picking up a steel rod, don't quite know what the correct size is yet, to straighten it out. I was thinking 11/16 since that is the closest to the custom sizes I keep seeing.

    A few upgrades I plan to/ will make.

    1. Rear sight is going to be moded so that it is windage adjustable, to compensate for that I will be replacing the front post with an AR-15 post site. The current plan will add about 5mm of height to the rear sight, but I am confident I will be able to compensate with the front site. We will see though.

    2. Install a Blackjack Buffer. This is actually already done, put the order in almost right after the parts kit arrived.

    If you have any tips on the two points of contention above, please let me know.

    IMG_20210301_170221633_HDR.jpg

  8. #8
    WildBillCody's Avatar
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    You can remove the tube on the triple tree all together. It is made separate, then you can replace it with an appropriate size one, might save you some time.
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  9. #9
    holescreek's Avatar
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    The BJ buffer is a waste even on a .308, much less on a x39. A 308 cetme carrier never touches the buffer except for extreme conditions like shooting suppressed with the wrong LP. I did a study on it last year with varying barrel lengths and LPS.

    Are you going to modify an existing cetme sight or go with an AR15 A3 style rear?

  10. #10
    WildBillCody's Avatar
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    Also, if you need a AR front sight post I can send you one or two.
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