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Discussion Starter · #1 ·
Hello,

Got a nickel boron BCG (full auto, 5.56) from a discount-tier company that I believe sources from Toolcraft. BCG appears to be out of spec somehow. When I received it (assembled) there was no movement in the bolt / cam pin. When I tried standard disassembly, I couldn't get the firing pin out either with gravity or knocking on a padded surface. Couldn't pull it out with my fingers or start it out with a nylon pick. Ended up having to pry it out forcibly with pliers. Same for the cam pin, had to rotate it and pull it out with needle nose pliers, couldn't do either with my hands. Cleaned it thoroughly, lubed it, tried to reassemble. Could not get the firing pin pack in. It is stopping somewhere inside or forward of the cam pin but short of the bolt face. No amount of reasonable pressure would get it through. Long story short, I tested all the parts by swapping them out with those from a 9310 Nitrided BCG, from the same manufacturer. Cam pin works fine in the substitute BCG. Firing pin works fine too. Bolt from the substitute BCG works fine in the nickel boron carrier. Yadda yadda, something is up with the bolt. Suspect the holes for the firing pin to pass through are outside of tolerances? Could that nickel boron coating have effed up the alignment of the relevant holes by .005 of an inch or something?

Gonna get them to replace the bolt but wondering if anyone has any experience with something similar or a stroke of genius piece of advice or theory.

Thanks in advance!
 

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Discussion Starter · #2 ·
That weird, I have never had anything like that. I assume you know the firing pin retaining pin comes out first, which I'm sure you did since it sounds like you have another bolt carrier group.
Thanks for the reply. Yes on the firing pin retaining pin. Here's how I should have described the weirdness of the problem: When I remove the bolt, I can pass the firing pin through it no problem. It seats as it should. When I stick the cam pin in the carrier, without the bolt, I can pass the firing pin through the holes in the cam pin too, no problem. But when I put the bolt in the carrier, and the cam pin in the bolt, something is not lining up perfectly, and the firing pin stops, HARD, 3/4 inch or so before it's fully seated. I tried rotating the cam pin 180 degrees, jiggling the cam pin while pushing the firing pin, lube, etc. No dice.
 

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Discussion Starter · #3 ·
I may not be fully understanding (MY bad), but I believe you only rotate the cam pin 90 degrees. I do not have a bolt/carrier right in front of me right now.
Yeah, you rotate 90 to fully assemble the bcg, but what I meant is flipping it 180 when first inserting the cam pin into the carrier, in case there was any difference between the opening on one side of the cam pin and the opening on the other.
 
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