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I finally received my upper, because of parts outages I opted for a 20" barrel, different brake and I did the assembly(first time I have ever messed with an upper receiver). Currently she is stove piping, it is getting better. I've put 36 rounds through it. First three cases stove piped and then three times more at random times.
The bolt is locking back. So from the other post I've read on stove piping I think a good spot to start would be the extractor.
So what are the pros and cons of polishing the extractor?
How forgiving is the part because I know I will make mistakes being the first time?
Should I just roll with it breaking itself in since the problem is getting incrementally better?
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Factory ammo? What does your brass look like, in particular the case head and rim?
Do you have an adjustable gas block?
There are several things that can cause FTEs. The three main culprits that come to my mind would be gas regulation, wrong buffer weight, or mechanical flaw with the extractor. There are other issues that could cause it too, but those are where I would start. I warn you however, that I make no claims of being a gunsmith. :p
Will it manually cycle rounds or snap caps just fine? If not, you probably have something going on in the bolt.
If it manually cycles just fine, then it might be overgassed. That would indicate too large of a gas port in the barrel, but could be remedied with an adjustable gas block. The wrong weight buffer can cause similar symptoms.
Have you removed the extractor and looked at the groove of the extractor claw for machining artifacts like a burr or something that would impede its grasp on the case rim? If it looks ok, it probably doesn't need to be polished. If it does not have enough tension to hold onto a case the way it should, it might need an o-ring around the extractor spring, but that would be weird for a new bolt. If it's a fresh spring, you ought to not even need the o-ring.
The only other thing I can think of is a bad ejector. They are a pain in the butt to remove and even more so to reinstall without a tool, though. If it comes to this, I will try to explain how I remove one without a bolt tool.
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Do you have a dremel? Or a bench grinder and felt wheel? If so, do it. You won't hurt it doing it carefully, and it pays off in the end. You'll appreciate having spent a little more time on your own build too. My two cents.
Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.
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08-01-2018, 03:47 AM
(This post was last modified: 08-01-2018, 03:51 AM by Msalm.)
When you say stove piping what exactly is the issue? Is the round jamming during the feeding cycle? Ive seen multiple Grendel ARs jam a round during the feeding cycle and a round ends up tilted upward with the base of the round caught on the underside of the ejector. The fix is very simple with just adding a slight chamfer on the lower portion of the ejector.
If it is an ejection/extraction issue, pick up an extractor from AA and put a proper one in. Ive reworked some but they can be a PITA at times...better to use the proper one off the bat.
