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Thread: 45 ACP Cetme Pistol Build

  1. #1
    holescreek's Avatar
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    45 ACP Cetme Pistol Build

    This is an ongoing project and I have lots of photos to upload.

    I figure that this will be my last (or at least next-to-last) Cetme build so I'm documenting it for future builders. Rhineland Arms sells a "kit" consisting of a 45 ACP barrel and a mag well adapter that holds a Thompson magazine in a Cetme/HK mag well. I've participated in threads where others have built Cetme's using these kits with varying degrees of success so I wanted to try one out for myself...with a twist. I want to build it as a pistol with a brace, and I want to do one version as a direct blowback and a second version (all the same pistol) as a delayed blowback so I can work out the kinks for each system.

    It took a couple of months to receive the kit from Rhineland but this was ordered at the beginning of the Covid shutdowns and that may have played a big role. Then there was a mix-up and I got the wrong barrel with the kit delaying it further.
    While I was waiting for the kit to arrive I bent the flat and started hacking on the parts to convert them for a pistol build.

    I cut the receiver back,

    DSCF7732.JPG

    Scribed lines under the cocking tube to remove the outer shell material to clear the trunnion,

    DSCF7734.JPG

    and used a cut-off wheel to slice through the shell to remove it.

    DSCF7736.JPG

  2. #2
    holescreek's Avatar
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    It just occurred to me while I was posting pics that I still need to drill the new access hole for the cocking handle pin in the cocking tube and I need to cut about half of the inner shell off where it fits into the receiver.

    Next task was to shorten the carrier tube 1-1/2" and weld it back together. I re-used the alignment pin from my recent .308 Cetme pistol build.

    DSCF7737.JPG

    DSCF7738.JPG

    DSCF7739.JPG

    During my last pistol build I spent some time investigating the buffer contact and found that the .308 wasn't making contact. I decided that since this is only using a 45acp that I had lots of room to play with and cut an inch off the rear of the receiver, making this a 1-pin receiver.

    DSCF7741.JPG

    DSCF7742.JPG

    DSCF7745.JPG

  3. #3
    holescreek's Avatar
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    I also removed 1-1/2" from the return spring guide rod and cut just enough spring off so that the carrier was able to contact the original buffer when pushed down over the return spring.

    At this point all I had to play with from the kit was the mag adapter, so I put it together to see how it felt.

    DSCF7747.JPG

    It's going to be interesting to see how well the cartridge feeds from the Thompson mag.

    DSCF7748.JPG

    DSCF7752.JPG

  4. #4
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    This is a very neat and interesting project. Can't wait to see more of your progress. Very cool!

    Are you going to have to make or modify a bolt head and extractor for the .45 ACP?
    Last edited by scottz63; 07-23-2020 at 07:31 PM.
    14EH AIT Instructor-PATRIOT Fire Control Enhanced Operator/Maintainer

  5. #5
    holescreek's Avatar
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    The 45acp and the .308 Winchester case heads are within a few thousandths of each other. The fit couldn't be better. The trunnion ramp needs some grinding to guide the cartridge into the chamber but I want to do that after the barrel is pressed in so I can test the feed before the trunnion is welded in.

    I blueprinted the Rhineland Thompson adapter last week to get a feel for where the cartridge is supposed to sit in the gun before the carrier pushes it forward. I had a bright idea that I was going to make my own adapter that used 45 acp Glock mags. After a couple days measuring and drawing in CAD it looks like the Glock mags are a no-go (at least on paper) due to the extreme feed angle and minimal rim exposure. I might give it a try in the future anyway to see if I can get lucky.

    DSCF7746.JPG

    I got the correct HK/Cetme barrel from Rhineland and am a little disappointed. The barrel is well machined and is actually nitrided but none of the diameters on the barrel are correct for a Cetme/HK build. Someone without a lathe could not use the barrel as it arrives. I'll get pics and dimensions up tomorrow.
    Last edited by holescreek; 07-23-2020 at 10:47 PM.

  6. #6
    7.62guy's Avatar
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    I always enjoy your builds but this one I'm really going to like. I have my H&K USC that I bought a lower for that takes M3 mags and they work very well in that application. I know it's not in a cetme but it would be another thirty round mag you could try. I also made the USC into a pistol and bought a suppressor for it when the Virus checks came out. I hope this works out well for you and if not I know you will just make it work. Have fun with the build because they are a lot of fun to shoot.
    For those who fought for it, freedom holds a flavor the protected will never know. Those who hammer their guns into plows-will plow for those who do not. Thomas Jefferson

  7. #7
    Senior Veteran sdk1968's Avatar
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    been waiting a long time to try this with their adapter vs the old blow back style we did in 2008.

    great looking work as always.
    say what you mean & mean what you say!
    TEC Tactical=SOT/07 i work there.

  8. #8
    holescreek's Avatar
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    Here's what the $189 Rhineland kit gets you. A 16.5" 45acp nitrided barrel and a hard anodized magazine well adapter:

    DSCF7766.JPG

    Close up of the adapter:

    DSCF7767.JPG

    The ejector on the top is spring loaded to drop when the carrier passes over it and raise for ejection:

    DSCF7768.JPG

    The problem with the barrel as it arrives is that the trunnion diameter is too large to press into a .866" diameter trunnion. It also comes with a large rim that's unusual to see on an HK/Cetme barrel.

    DSCF7759.JPG

    I was originally going to cut the rim off so I could press the barrel through like a standard Cetme but after checking dimensions determined that the rim was designed to provide exactly .015" of barrel face above the trunnion rim when fully inserted. It was a novel idea (for me) to press the trunnion over the barrel stub into the rim but I figured I'd give it a try anyway after I trammed the barrel in on the lathe and fixed the diameter of the stub.

    DSCF7761.JPG

    DSCF7764.JPG

    DSCF7765.JPG

    I found a study online where the 45acp was tested through a barrel that was cut back 1" between tests. Maximum velocity was achieved at 15" (longer barrels slowed the bullet down and shorter barrels weren't as fast). However, best accuracy was achieved at 11" with the best standard deviation. So while I was on the lathe I flipped the barrel around and cut the length down to 10.5", after tramming the bore concentric I added the threads back for the muzzle device and turned the diameter down for the front sight base. I could've gone an inch shorter and been OK, but for what this pistol will be used for an inch won't matter.

    I almost forgot to add that the rim on the barrel slightly interferes with the rear hand guard ferrule to keep it from fitting all the way into the rim on the front of the trunnion. Just something to watch out for.
    Last edited by holescreek; 07-24-2020 at 03:36 PM.

  9. #9
    holescreek's Avatar
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    Quote Originally Posted by 7.62guy View Post
    I always enjoy your builds but this one I'm really going to like. I have my H&K USC that I bought a lower for that takes M3 mags and they work very well in that application. I know it's not in a cetme but it would be another thirty round mag you could try. I also made the USC into a pistol and bought a suppressor for it when the Virus checks came out. I hope this works out well for you and if not I know you will just make it work. Have fun with the build because they are a lot of fun to shoot.
    Can you post some pics of your USC with the M3 mags? I've been googling it but not getting any visuals.

    Website with barrel length test results: https://www.internationalsportsman.c...th-for-45-acp/

    Video on barrel length tests:
    Last edited by holescreek; 07-24-2020 at 09:17 PM.

  10. #10
    7.62guy's Avatar
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    Here are a couple I had laying around here. I'll get some a little better as soon as I find and charge the camera.
    Attached Images Attached Images
    For those who fought for it, freedom holds a flavor the protected will never know. Those who hammer their guns into plows-will plow for those who do not. Thomas Jefferson

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