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Posted: 4/18/2011 9:28:19 AM EDT
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Here's some background I put together a BCM 16" middy upper with LMT lower and Fail Zero BCG.The first time I went out and put 60 rds through it I had 3 FTE double feeds, second time I went out I only had 1 double feed for 120rds. I used 7 different Pmags and none of the FTEs happened with the same magazine.
Would upgrading the extractor spring be a quick fix to this isssue? Thanks |
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What ammo were you shooting? If it's Tula... New ammo, look no further. If it isn't Tula, continue below... Do you have another bolt carrier group you can try? If you don't or if it works fine with the other carrier, try replacing the spring and o-ring with the upgrade kit from BCM. |
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by double feed you mean the spent casing is still in the chamber or only partially extracted when the next round attempts to be loaded?
then yes, you could try upgrading the extractor spring or adding an o-ring as a quick workaround to see if the problem goes away. ironically, it sounds like your "Fail-Zero" is a "Fail-Four". 
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How much lubricant does the bolt have? Sometimes a new build can bind slightly until the parts settle in. This isn't common but a possibility. Our department uses surplus Colt M16a1 rifles converted back to semi. The bolts are pretty wet.
Another thing to consider is to load one round of the ammo you're using in each mag and fire it. Shoot quite a bit to make sure each round locks your bolt back. This will help determine if the ammo you're using is or isn't pushing the bolt carrier assembly back far enough. The positive side to this is you can practice reloading. If your gun was built correctly, the common things to consider are a thorough cleaning, good ammo, and magazines. A few other things besides cleaning and ammo, try a few different AR mags as well as make sure the gas rings are off set, so you're not losing gas pressure. |
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Quoted:
The ammo I've been using is 62gr pmc xtac, I don't have another BCG at the moment to try. The BCM upgrade kit is what I was thinking about buying but I just wanted to get some input on here first to rather or not that would solve the problem. X-Tac ammo is good stuff. I'm willing to bet its an extractor problem. Try another bolt in your rifle if you have one or can borrow one to see if that fixes things. |
| Yes I'll admit I took a big sip of the Failzero koolaid but if I can fix the problem for 5 dollars buy upgrading the extractor it'll still be worth it since it's so easy to clean. As far as using lube I've still not put any on the BCG yet. One other thing I thought that may cause it was if I didn't line the low profile gas block up correctly with the gas port but I figured if that was the problem I would of have a lot more issues than just 4 FTE's after almost 200rds, and I have performed the short stroking check where you load one round in the magazine to make the bolt lock back and it does each time. So I'm hoping it's just the extractor |
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Fail zero bolt and low profile gas block ... funny how the after market stuff always causes problems..
Try throwing a stock BCM BCG with some lube and the problem will go away... or use some of that Kool-aid you drank and splash it on the BCG to get some lube in there.... Did you built the upper or buy it and add the gas block yourself? |
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Quoted: Yes I'll admit I took a big sip of the Failzero koolaid but if I can fix the problem for 5 dollars buy upgrading the extractor it'll still be worth it since it's so easy to clean. As far as using lube I've still not put any on the BCG yet. One other thing I thought that may cause it was if I didn't line the low profile gas block up correctly with the gas port but I figured if that was the problem I would of have a lot more issues than just 4 FTE's after almost 200rds, and I have performed the short stroking check where you load one round in the magazine to make the bolt lock back and it does each time. So I'm hoping it's just the extractor If the problem was not enough gas, it would be short-stroking or not unlocking the bolt at all. This wouldn't cause problems with failing to extract. At least, not to my knowledge. |
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