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Thread: CETME-47 (CETME in 7.62x39)

  1. #61
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    Nice! You got it throwing rounds down range.
    14EH AIT Instructor-PATRIOT Fire Control Enhanced Operator/Maintainer

  2. #62
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    Quote Originally Posted by scottz63 View Post
    Nice! You got it throwing rounds down range.
    Yeah, it was a nice change of pace running through a few mags without issues. Hopefully grinding down that feed ramp a little bit makes the gun a little less mag specific. I ran through Holescreeks build he posted earlier and it sounds like he was having the same feeding issue, but I don't think he posted what he changed, maybe it was him switching to tapco mags.

  3. #63
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    Well I am officially shelving this build since I cannot seem to figure out what is causing the feeding issues. I took down that feed ramp a bit and a still have the same issue at random. One mag will do it feeding from the left, another will do it feeding from the right. A mag will work flawlessly, reload it and then it jams again. I can not find any measurable difference between a mag that works and a mag that doesn't, so it doesn't seem to be a mag issue. I'll still bring it to the range and if I figure out the issue I will be sure to update this thread.

  4. #64
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    Well I finally have a good update to announce and can say the gun runs right and is ready to be parkerized, once I finally get may parking setup completed. I took the advice that a few other posted and blue dykemed all of the moving parts of the gun. I found that the back of the Bolt Carrier was rubbing really bad over the hammer, the ejector was rubbing on the tract in the bolt head, and the front of the carrier top tube was rubbing in the cocking tube. To help fix all these issues I printed a shortened version of Triple Tacos 3d Mandrel, cut the welds holding the rails to the trunnion and re pressed everything. I also used a 600 grit belt and my belt sander to smooth out a lot of the moving surfaces to help parts glide. This was focused on the hammer face to give it a little more curve, the bottom of the bolt carrier and the front of the carrier where it meets the charging handle support. I didn’t remove much, only enough to remove any slight surface marks in the metal.

    Next I looked at the mag-well adapter and magazines. Based on the wear marks the mags sat a little high in the front and were slightly tilted to the left. For the mags sitting high, I reworked the front and back catch so the front sat a little lower and the back sat a little higher. The final dimensions came out to be 8mm down from the top in the front and 19mm down from the top in the back. This allows the feed lips to sit as close to the bottom of the bolt/ carrier as possible. Unfortunately the mags leaning in the mag well was from the magwell being canted from a bad initial press so to fix that I ground a little off the right side of the adapter and added a small blob of weld to the left side. That took care of the canting issue. Lastly I had a NOS G3 recoil spring that I swapped out for the old worn CETME spring that had taken about an 1” worth of set.

    I took it to the range and it cycled trough the Steel Bulgarian mags without issue, the unknown maker surplus mag I had was still having issue which brings me to the final change I made, which was to the feed ramps on the AK mag its self. I think the issue I was having all along was a combination of the mag not sitting at the right angle due to the adapter and the feed ramp on the ak mag. If those ramps were just slightly pointed in at the wrong angle it would cause the round to point too far over when it was getting fed causing the issue. On an AK the bullet would be in the chamber before this was an issue but since this gun has the bullet free floating just a bit, it was enough to cause feed issues. This realistically may be a specific issue with my gun as it doesn’t sound like the other builders were having the same problem or maybe their mag adapter compensated for it. So on the steel mags I was having feed issues with I took a pair of pliers and slightly bent that angle out just a little bit. If I were going to build another one of these x39 guns I would probably seriously look at removing a little bit of the trunnion so I could seat the mags in closer to the chamber and cut the rails back the same distance to avoid having to mod the mag well.

    Overall, I think the changes to the mag well adapter, mag feed angle, and mag feed lips were what really made the most difference, the polishing of the contact surfaces was more to reduce drag on the bolt carrier when charging than to help solve any feeding issues.

    Photos are just a couple shots of the mag adapter, how the mag sits under the bolt, and a couple of the magazine feed guides I am referring to. Mag on the left is the unmodified Bulgarian mag, mag on the right is the unknown surplus mag with the left feed guide bent out a bit.

    IMG_20210913_160342567.jpg

    IMG_20210913_160355773.jpg

    IMG_20210913_160453284.jpg

    IMG_20210913_160653434.jpg

    IMG_20210913_161031588.jpg

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