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Hello everyone, I have been having an issue that has been plaguing me for the last few months. I own a CETME C308 from century arms that has functioned flawlessly for the first 200 rounds. All of the sudden when I changed ammo brands, the bolt begins to lock back behind the hammer. The the initial ammo I used for it was German 147 grain surplus with the cupro jacket in. The ammo that I was using when the locking of the bolt began was 147 grain american marksmen 7.62x51. One thing I noticed with the ammo is that it came out extremely dirty compared to other ammunition for other calibers. I cleaned the gun and have gotten flakes of some sort of residue from the trunnion. I am uncertain of this being the issue. Another question I have is if whether or not the bolt head is supposed to go past the cocked hammer. The CETME C308 is, as we all know, made from surplus parts that likely used a preservant. I never gave the gun an initial cleaning when I first got it and I don't believe I have ever cleaned the trunnion. I should mention that this my C308 is part of the generation that uses PTR parts. Any and all help on the matter would be greatly appreciated.

Thank you! I'm ready to be shamed if it's a simply issue that requires a simple solution.
 

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I can’t assist you with your problematic bolt but I can welcome you to the forum!

We have members here who know the CETME/G3 inside out and I’m sure they’ll soon weigh-in with suggestions. Good luck!
 

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Given that the CETME is a delayed blowback type action, my first guess is that the ammo that has given you problems, the American Marksman brand, may use a powder with a burn rate different than the design of the CETME system called for. You may wish to throughly clean and lube the entire mechanism and then try another brand or two of ammo to test this possibility. I do not think that it is normal for the bolt to end up it's recoil behind the cocked hammer. That alone indicates to me that there is more rearward force during operation than intended for the gun. I am no expect on this matter, maybe soem other readers will offer their input.
 

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You need to look very closely at your buffer. If it has collapsed it will allow your bolt to travel too far to the rear. It is also possible that the ammo you're using is too hot or as Moulainville noted it may have a different pressure curve that is creating too much bolt velocity. That will cause the bolt to impact the buffer harder and possibly travel further to the rear where it can catch the hammer.
In the original layout the hammer was captured by the trip sear which holds the hammer down low enough that the bolt can't catch it. With the ATF requirements that don't allow the trip sear the hammer sits a little higher where it may catch the bolt or carrier if it over travels.
Try other ammo before you get too deep but make sure the buffer is ok too.
Hope that helps

Frank
 

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You need to look very closely at your buffer. If it has collapsed it will allow your bolt to travel too far to the rear. It is also possible that the ammo you're using is too hot or as Moulainville noted it may have a different pressure curve that is creating too much bolt velocity. That will cause the bolt to impact the buffer harder and possibly travel further to the rear where it can catch the hammer.
In the original layout the hammer was captured by the trip sear which holds the hammer down low enough that the bolt can't catch it. With the ATF requirements that don't allow the trip sear the hammer sits a little higher where it may catch the bolt or carrier if it over travels.
Try other ammo before you get too deep but make sure the buffer is ok too.
Hope that helps

Frank
Tried this, it was helpful thanks frank


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Its typically a combination of parts etc. What your experiencing is not uncommon. First, NATO spec 762x51 ammo is what this rifle is designed. It's more robust, intentionally. The recoil buffers in these are metallic capped, thick rubber and three pieces aligned. Most as almost all of them are completely shot and hard as a rock and need replacement. This condition will beat the mhit out of the rifle and your shoulder, making for a less than desired experience. This is why the collapsible buttstock assembly by HK are called a meat grinder....they will pulverize you into a Cortisone injection.

Look at it this way, the Germans did not intend to over-engineer everything, but it's just what they aspire towards. Think Panzer Tanks.

If you PM me your number I'll give you a call and help you in any way, so your back up and running.
 

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Have you looked at the buffer?

If it looks original, there are replacement recoil buffer parts available that may solve the problem.

 

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The best solution is the Bill Springfield Spring as it reduces recoil, the Plastic buffers sold as one piece are hard and unforgiving and may actually fracture.
Can you swap a complete HK-style spring buffer with a Cetme C-style rubber buffer, or just use the HK spring in the Cetme housing?
 

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A fellow many moons ago made a neat tool to open the buffer he used a castle nut and piece of bar stock then was able to use a wrench or ratchet to open that tight son of a gun up
Purple Rectangle Creative arts Material property Magenta
 
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