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Posted: 1/13/2005 6:20:48 PM EDT
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I have a CDNN M-16 type upper that I put together with a RRA Bolt Carrier. What am I missing here, the bolt will not close with a round in the chamber. I have swapped bolts out with my other RRA rifle. I know I read here that any bolt should work, but that is not the case. The rounds that I tried to chamber were 5.56 not 223 Joe |
Step one.... clean and lube per the TM, and clean the chamber with a chamber brush. Inspect chamber, and locking lugs area to ensure there is no debris. Step two, ensure bolt will close and lock on an empty chamber with no issues. Step three, load a round, and close the bolt. If it will not lock, then carry to a smith for headspace check, perform your own with the correct go/nogo/field gauges, or return the upper to CDNN. |
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The upper was already together, from what they advertize it was surplus. It looks great and I have been waiting to fire it, waiting on the bolt carrier. Put the carrier in and it's a no go, then tried my other carrier and no go also. This is probably a M-16 upper. Joe |
told ya I did'nt know much about that  I've been meaning to read that stuff just never got around to it, I'll do my time there tomorrow
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Two possibilities (since you said you thoroughly cleaned the chamber): 1) Bad/stuck/out of spec extractor This can keep the extractor from snapping over the rim of the cartridge, and thus keep the bolt from going in far enough to let it turn and lock. 2) Out of spec chamber The cartridge dimensions for .223 and 5.56mm are the same, so it doesn't matter which you used. The point is that you tried a variety of different, reliable brands, and none of them worked. I thought about troubleshooting your bolt to prove what part may be causing the problem, but here's the simplest thing to do: I'd borrow a friend's bolt and see if it will chamber with that bolt. DO NOT SHOOT IT WITH YOUR FRIEND'S BOLT. Sure, they're supposed to be interchangable, but CHECK HEADSPACE WITH YOUR FRIEND'S BOLT BEFORE EVEN THINKING ABOUT SHOOTING WITH IT. The point here is to see if your bolt is at fault, not to hijack your buddy's bolt. If it works with his bolt, then it's obviously something to do with your bolt. If it doesn't work with either bolt, then it's the chamber. |
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Also check the Ejector to make sure it is not stuck or damaged. Disassemble a bolt take out the extractor and the ejector reassemble into the carrier and see if the bolt will close. Without the bolt does the cartridge drop into the chamber all the way? How far does the bolt stay out of battery? Picture? |
The throat dimensions differ between .223 and 5.56. The throat of .223 is tighter and can cause feeding problems using 5.56 ammo in a .223 chamber. |
This isnt actually correct.... at least part of it. From the ammo oracle:
You wont have a potential problem *feeding* 5.56 ammo into a .223 SAAMI chamber..... since the ammo is dimensionally exactly the same. What you could potentially have... is higher *pressure* when fired... resulting in popped primers, case failures, and potential for poor extraction. Besides... this is a M16 upper... with a chrome lined NATO chamber.... and irregardless isnt part of the problem. 
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