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Posted: 12/10/2003 9:58:41 AM EDT
Function firing and sighting in 3 AR15 uppers.

Have a problem with only 1.

Description. Standard 20 inch barrel. A2 flash suppressor. Painted it myself. Have now used a thin sharp piece of metal and punched through the exposed gas tube opening in case there was any paint accidentally sprayed into the gas tube port. THis was done after experiencing the problems that will be described.

Using the same magazine. Using home reloads. Using factory.

Original problems were failure to fire reloads, failure to extract, the usual. Replaced firing pin. Replaced extractor with aftermarket one and the spring is a later model with the blue plastic dot.

Went to range with Winchester factory. No problem extracting. Sometimes a light primer strike on factory ammo. Had replaced firing pin with another factory pin. Should I try a third factory pin or what? The more significant problem is failure to pick up a round at all and to insert it in the chamber. What would happen is that somewhere in the middle of a magazine, I would "fire". There would be no round in the chamber. Does this indicate that the recoil buffer spring in this "new upper" should be replaced.

Further information. I used the same lower receiver with three uppers (And yes, for those squinty eyed people out there, it is registered under my name in California). When I worked with a couple of Bushmaster short barreled uppers, the report and recoil was a bit more noticeable.

Each of the uppers is complete. Each has its own bolt, bolt carrier, etc.

Thanks for any assistance.
Link Posted: 12/10/2003 6:57:37 PM EDT
Please tell me that you pulled the upper apart before you started to paint everything, hence things were painted in pieces, and then re-assembled after the moly paint had cured. If you just hung the complete upper by a string and started painting, then I think you may have created your own problem. Depending on what type of paint you used, you may be able to drop all the loose upper parts in a solvent tank, and remove the paint. Without seeing the rifle, my guess is that the inside bearing surfaces of the upper are littered with paint flakes/rough surfaces, and this is binding the carrier travel threw the upper.
Link Posted: 12/10/2003 8:36:33 PM EDT
Easy enough to answer. Removed the bolt carrier assembly. closed dust cover. protected inside of barrel. No paint on inside. Have painted other ar15s, etc. in the past. Typically, gray special primer and then special cameo paint. You have caused me to think it through further. The cause can't be the recoil buffer spring because it works fine with two other uppers, including another painted dissipator. Everything locks up fine. I may have solved the problem with a "pin" cleanout of the gas tube vent. I have spare complete bolt/bolt carrier/charging handle setups and I will rotate them in if the rifle doesn't work. The problem is that a round is not being picked up and put into the chamber.
Link Posted: 12/11/2003 8:24:43 PM EDT
There is a good chance that the round not being picked up is a result of short recoil, could also be a result of a bad mag. Basically, short recoil would cause the bolt/carrier to not be pushed back far enough to pick up a new round, just far enough to eject the fired case. Added friction in the inside of the upper (due to paint?) could cause this. Or if the gas tube end had been plugged up, that would give you the same results. I think you can rule out anything on your lower giving you problems since it does work with the other two uppers. As for the light primer strikes, it may be possible the bolt is out of spec and not allowing the pin to go forward far enough to hit the primer. An obstruction or heavy fouling in the firing pin channel could also be the issue as well.
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