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Posted: 3/7/2017 10:44:26 PM EDT
| I am putting together a 603 clone and ran into a problem I haven't seen before and wanted to get some opinions on it. It is a 603 upper mounted to a modern pencil barrel 5.56 20"barrel. When I dropped the BCG into the upper I expected the BCG to engage the upper and lock in. But to my surprise it just slammed against it , metal on metal. Moving it back and forth several times by hand it would not go in. After installing a donor lower with the buffer and spring installed I pulled back the CH and released and the BCG slammed home like it should. The gas tube appears straight and no obstructions can be found. I have tried several different BCG' with the same result and they all work fine in other uppers. Any thoughts ? |
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Take the bolt out of the carrier. Try it.
If it still sucks, it's the gas key and tube mating up. With the bolt still out of the carrier, use your pinky and rest the tip on the exposed gas tube as you slide the bolt in the upper (no charging handle). Go in and out. You will feel the gas tube move slightly. Example : when you slide it in, and then back out, if the gas tube moves down (away from the top rail) as you pull the carrier out you need to bend it towards the rail, and same goes for any other movement. Use your noggon. If it mates nice, and smooth (snug but not very tight) put the bolt in the carrier and try again. Also could be very stiff gas rings in the bcg as well. It should all fit together a little snug. Look how the bolt locks and aligns with the barrel extension. If it's still smooth, put the charging handle in and try it. Process of elimination. |
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Thank's guys, I think I found the culprit. I tried everything recommended and still had issues with the BCG. I wound up pulling the gas tube I THOUGHT was straight and found that it was anything but. It was a old tube from a M-16 parts kit I bought years ago and found it was bent down and to the left. After seeing the damage to the end of the tube from me slamming it over and over ( well a few times ) and not knowing the correct bend angle, I'm going to Core-15 tomorrow ( 5 miles up the road ) and pick up a new one. Will post up hopefully good news tomorrow night on a smooth running upper. I appreciate the help.
Thank's again. |
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