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Posted: 3/21/2009 12:57:19 PM EDT
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I know this may seem like a silly question or a common problem but here goes.
I have an SBR that is failing to extract a case about every 2-4 rounds. Sometimes it runs fine with no issues. The gun will fire and fail to extract and pick up another round off the mag and jam up. My set up: 10" upper (unknown mfg - bought from the EE) DPMS M16 BCG bought new Superior Arms lower registered on a F1 MagPul UBR stock with a regular carbine buffer What should I be looking at replacing first? I really like this set-up .. I just need to get it running reliably. OH and I have a SureFire FA-556-212 silencer waiting for a F4 and it will be used almost exclusively on this gun. Suggestions? Thanks. |
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Had that problem once with my 11.5, got one of these and no more problems. http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20%203pack.htm |
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Actually perform this test before you do anything. Put one round in the magazine, chamber, fire and then check to make sure the bolt catch is engaging the BCG and locking it back. If it doesn't, then you need to put a lighter weight buffer in it (like a standard buffer) or you need to shoot ammo with more "blow back power".
Also I don't know if you can do this, but putting a sound suppressor on the end of the barrel increases blow back. I have some Wolf and UMC ammo that won't run unless I either put a standard buffer in, or a suppressor on the end of my barrel. Oh and I'm shooting an 11.5" barrel. HTH! 
ETA: It doesn't sound like a bolt bounce problem, so I think a heavier buffer will only make things worse. Your mileage may vary though. |
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Quoted:
Actually perform this test before you do anything. Put one round in the magazine, chamber, fire and then check to make sure the bolt catch is engaging the BCG and locking it back. If it doesn't, then you need to put a lighter weight buffer in it (like a standard buffer) or you need to shoot ammo with more "blow back power". Also I don't know if you can do this, but putting a sound suppressor on the end of the barrel increases blow back. I have some Wolf and UMC ammo that won't run unless I either put a standard buffer in, or a suppressor on the end of my barrel. Oh and I'm shooting an 11.5" barrel. HTH!
ETA: It doesn't sound like a bolt bounce problem, so I think a heavier buffer will only make things worse. Your mileage may vary though. currently running a standard buffer. already checked it to make sure it locks back on a single round. PASSED that test. I am waiting on a F4 and I will have a suppressor on it come about June? (just sent in the papers) different extractor spring maybe? |
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Quoted:
In that case it's probably bolt bounce. Put a heavier buffer in it, either a H or a H2. I doubt you'll need a H3. I thought bolt bounce referred to slamming home hard enough to knock it back out of battery? If that was the case how could it be jammed up with a failure to extract and a live round trying to feed? just trying to understand and make sure we are on the same wavelength. |
| The most likely cause of your failed extraction is a weak extractor spring. It is also the cheapest fix. Get the extractor spring upgrade 3 pack for under $15 and give it a try. I cured my 11.5s extraction problems with just the spring and insert, I didn't even use the donut. |
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Quoted:
The most likely cause of your failed extraction is a weak extractor spring. It is also the cheapest fix. Get the extractor spring upgrade 3 pack for under $15 and give it a try. I cured my 11.5s extraction problems with just the spring and insert, I didn't even use the donut. how exactly is that "donut" supposed to work? I am probably going to order both the spring kit and then the H buffer if the spring doesn't do it. I know this sounds stupid .. but this is the first shorty I've ever really had problems with and I used to have a 11.5" RDIAS host that ran perfectly on auto from round 1. 
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My 11.5 ran perfectly too up until the extractor spring went tits up. It ran fine with the standard carbine buffer it came factory with and the endine rate reducer I bought to try to reduce gas blow back when shooting suppressed. When the extractor spring went, it started doing exactly what you describe. As for the "donut", I would imagine that it simply gives your extractor more spine, in other words it increases extractor tension. Give us an update when you install and test the spring kit, I'd like to know if it fixes your problem. |
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Quoted:
My 11.5 ran perfectly too up until the extractor spring went tits up. It ran fine with the standard carbine buffer it came factory with and the endine rate reducer I bought to try to reduce gas blow back when shooting suppressed. When the extractor spring went, it started doing exactly what you describe. As for the "donut", I would imagine that it simply gives your extractor more spine, in other words it increases extractor tension. Give us an update when you install and test the spring kit, I'd like to know if it fixes your problem. will do! expect an update as soon as BCM can ship me the parts! 
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Quoted:
Quoted:
In that case it's probably bolt bounce. Put a heavier buffer in it, either a H or a H2. I doubt you'll need a H3. I thought bolt bounce referred to slamming home hard enough to knock it back out of battery? If that was the case how could it be jammed up with a failure to extract and a live round trying to feed? just trying to understand and make sure we are on the same wavelength. Sorry I forgot this was an "extraction" problem. I read too many threads... 
Anyway a heavier buffer will slow the BCG down and may help, however it sounds more like an extractor problem, or possibly a bad magazine (probably not though.) I would definitely try the stronger extractor springs, or maybe another bolt if you have one laying around? Good luck!
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