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Discussion Starter · #1 ·
I acquired a C93 a few months ago with a serial number of C93052XX

I was curious if anyone could help me with any info pointing towards when this one was released. Is this one of the first ones?

It certainly does have jamming issues and a bolt Gap of .023. Failure to feed and failure to eject. The ejector spring was replaced after discovering it was bent but that made no different. spend casing are barley trickling out. A smith is currently looking at the gas system but I'm afraid he isn't experienced with the C93 creation! Ive mentioned everything that I have read to him so I will wait and see!

There is another for sale with a serial number of C93148XX. I assume this would be one of the later ones? The furniture looked refinished and the receiver also looked slightly different color wise.

Ive seen threads with the lower bolt gap but not too many address the larger gap issues. Just trying to understand my options for repair and selecting a good one in the future.

Any help would be appreciated.
 

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The Librarian
MP5-N and HK23E-K
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It's a parts kit build. No gas system. It's a delayed blow back. Bolt Gap at 18 (.018") is optimal and .004"-.020" would be the range you want to say in for a 93. I'd also replace the entire lower trigger group.
 

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The Librarian
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Not really. It depends. Some work perfectly, others not so much. If you have another 90's series gun, you can swap parts and start dialing in on what the problems are. Also, complete your profile. Maybe someone in your state can lend a hand. I'm in NE PA.

Jamming issues are sometime magazine or ammo related issued. FTE are ejector or ejector spring, Extractor or extractor spring related so try those first. Lower trigger groups and housing would be the second things to look at.

Generally, larger bolt gap will result in more energy being transferred to the carrier yielding more felt recoil and receiver marks from caused by the bolt head rollers.


....and buy the way, a -8 roller would bring that bolt gap from .023" to .020", but measure the current set of rollers first and see it there are a standard size 0 (8mm).
 

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Discussion Starter · #5 ·
Thanks for the info. The extractor spring was replaced and it had the same issue. I will try different mags and ammo next when I get it out the shop.
 

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The Librarian
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I had better picture, but can't find it so this will have to do.



Make sure the ejector lines up properly with the bolt head.
 

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Also check the height of the ejector in the slot in the bolt head. As seen in Oicani's pic, the ejector should ride close to the top of the slot. Loe position can/will cause weak ejection.
 

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Discussion Starter · #9 ·
Also check the height of the ejector in the slot in the bolt head. As seen in Oicani's pic, the ejector should ride close to the top of the slot. Low position can/will cause weak ejection.
After seeing that picture I suspect that could be one of my issues. I'm fairly certain that mine sits lower. If that is the case, is there a fix? Can it be modified or will I just need to go with a new trigger group as mentioned before.
 

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Start with some -4 rollers to get your gap in range. Your bolt may be delaying in unlocking moving rearward without enough force to eject and strip the next round. This is the cheap place to start.
 

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The Librarian
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But, measure the rollers you have first. See exactly where you're starting off at.
 
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