I concurr after the ink test that the upper is tweaked along the center axis from torque.
Maybe the MFG will help you out with another stripped upper.
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I concurr after the ink test that the upper is tweaked along the center axis from torque.
Maybe the MFG will help you out with another stripped upper.
To properly check the BCG fit, you need to disassemble the BCG and insert the carrier only. I would check to see if the tube is too high or low rather than left or right.
In addition the clamshell is not correct for a MUR and it may have gotten tweaked somehow.
Have you tried the carrier alone it the upper receiver? (No bolt, FP OR CAM pin) to see if the binding is between the carrier key and gas tube?
If it moves freely then the binding is between the bolt and bbl extension.
So I pulled the gas block to put Sharpie all around it and check the alignment. Here are the results, using a stripped carrier, like IG suggested:
Top
http://i546.photobucket.com/albums/h...psb8be1295.jpg
Left side
http://i546.photobucket.com/albums/h...psd6ee72df.jpg
Right side
http://i546.photobucket.com/albums/h...psb7d16a10.jpg
Moving it back and forth, I did notice that it is a bit smoother when it's just the carrier. I can feel when the carrier key come into contact with the gas tube, although it's so faint that I can't imagine it would be what's stopping the carrier when pushed forward by the buffer. I recorded 2 videos, with and without the bolt installed, but I don't know if they'll be at all useful. They're uploading now.
After re-installing it, I did my cycle-test again. It made it further before locking up, this time it seized up on round #14.
How many rounds total in this setup?
Without any additional issues, the wear alone wouldn't be a concern. Some rub more than others and show what looks like heavy wear early on. The MUR receivers are made to tighter tolerance than regular M4 receivers... it's common for them to fit barrel extensions, takedown pins, and even carriers much more snugly (downright stiffly sometimes). I suspect you've simply got a combination of parts that are fitting a bit too tight. Since this is a home-build and your options are pretty limited, I would shoot it for another 200 rounds and see if it "breaks in." I bet it will. I would suggest adding an XP spring, but I don't know enough about the A5 system to know if that's even an option.
ARs should be fully drop-in functional from round one, but just because one hiccups a bit when it's brand new doesn't mean it won't be a perfectly reliable gun.
70 rounds. This was my first time firing it, so I went to the range to sight in my scope and follow Compass Lake Engineering's recommended break-in procedure.
Your not SOL. Go shoot the gun, get 200 rds through the upper and see how it is doing. If it's still tight you can heat up the lower rail below the dust cover with a heat gun. Not a torch but a heat gun.
Then run the carrier back and forth as it cools. Heat it up to 350 to 400 degrees. It will not damage the upper at those temps. Make sure and run the carrier as it cools. That section of the rail will move out and away from the carrier giving the carrier space to move in the future.
Make sure and use a insert in the future.
I got ahold of Vltor support today, and the representative I spoke with recommended that I send it in. I'll take it apart this weekend to send it off and see about putting the barrel in a different upper to find out if the extension is off.