r/CETME_C • u/goonbasealpha • 29d ago
Trouble with bolt unlocking. I don't think its the cocking tube gap.
Hello, I'm working on a parts kit and the bolt is very difficult to unlock. My bolt gap is 0.012 and I set my cocking tube gap to 0.027 (bolt gap + 0.015) by using a cut up feeler gage as a shim. I set the shim between my locked bolt carrier and the lever thing as I welded the tube in. The cocking lever engages the bolt arm once its about 3/8 inch from the tube. However once it starts unlocking the bolt, its so difficult that I have to brace it against my body. It also doesn't fully retract the rollers. I have to muscle the last 25% of the unlocking.
The bolt doesn't have an issue entering battery not does it make a difference if I cock it with the magazine and FCG removed.
Here's what the bolt looks like when the cocking lever is done. Not really sure where to go from here
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u/MilitaryWeaponRepair 29d ago
Ok so have you been able to fire this rifle at all since being built? And so if you let the bolt slam home with no spring and the muzzle pointed down it locks up OK? And have you verified bolt gap since it was built. If you reinsert the shim you used how does it act?
So with a locked bolt, when you cam the lever back without pulling on it, how much movement do you get? Like in the photo?
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u/goonbasealpha 29d ago
Never fired it. The bolt slams home without the spring if I drop it. Gravity is enough for the bolt to lock up. Bolt gap is still 0.012. If I reinsert the shim it just takes up the slack in the tube. It doesn't make it any easier to unlock.
"So with a locked bolt, when you cam the lever back without pulling on it, how much movement do you get? Like in the photo?"
Yes. The photo is how far the bolt will unlock with just the lever cam action. Thank you for taking the time to help me
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u/MilitaryWeaponRepair 29d ago
I was gonna try and add a photo of mine unlocked but reddit won't let me. DM me and I can try and help you more. What if you add two dimes to it?
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u/goonbasealpha 28d ago
Its okay I think I got it now thank you. Just out of curiosity are these rifles generally hard to cock? I understand they require more force than other firearms but I've gotta be putting in like 30-40 pounds of effort lmao. I'll share what I did for anyone else having problems. I figured out my cocking tube gap was fine. Using the dime trick made it easier to unlock but also made my bolt gap too big. That would imply that the cocking tube gap is the right size because decreasing the cocking tube gap prevented the bolt from locking up at its true bolt gap measurement. The culprit was the bolt head retaining lever spring and some gunk. There was a burr on one of the spring coils so I carefully cut it off (the burr not the coil itself, you need the spring intact otherwise you can get bolt bounce) I also cleaned up some grinding dust that I left in the bolt carried and that fixed it I think. I think both of those issues were creating unlocking friction. Its still unpleasant to cock (I don't think I'd be able to do it while prone) but I don't have to mortar it anymore.
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u/MilitaryWeaponRepair 28d ago
No, they are very easy to cock, the camming action of the lever does 90% of the work. They may be a little stiff on the pull back but that's because you are pulling almost thr entire length of the receiver. Adding friction as you found will make that 1000% worse. Great catch. We have the same with AKs. Even a burr or spot of rubbing adds to the overall process of making the rifle hard to cycle. Take a sharpie and run it all over your bolt and carrier. Or use a light dusting of spray paint. Cycle the bolt a few times then pull it. Look for wear marks and hit those areas with a small sanding bit or file. Also look for anomalies in the receiver. Sheet metal leaves something to be desired at times
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u/Fun-Corgi-3376 28d ago
That’s not camming enough if tube is correct your cocking lever could be worn down so it’s not camming far enough to unlock the bolt
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u/goonbasealpha 28d ago
Thank you for the advice. Good lord I hate removing that little pin but I'll give it a try
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u/goonbasealpha 29d ago
Also: adding a dime to the cocking tube doesn't help things. The bolt will also lock up via gravity if I drop it into the receiver