Problem with AR15

[Aces and 8s]

Forgot to take pictures, but not sure they would help in this case :\

Everything LOOKS find to the naked eye.

[ProtectThe2nd]

Check for hammer dragging on carrier
Look for witness marks
Bent hammer pin?

That "gritty" noise you talked about sounds like parts dragging
Loose firing pin cotter key
Cam pin
Bent hammer
Bent buffer tube

[billped]

Check the Fetzer valve.

[oilcanhenry]

Check the Fetzer valve.

Yeah. Its either that, or the shoulder thing that goes up!

[Aces and 8s]

Check for hammer dragging on carrier
Look for witness marks
Bent hammer pin?

It definitely seems and feels like the BCG is dragging on the hammer. But, his upper doesn't do it on my lower, and my upper doesn't do it on his lower, so odd.

I couldn't try his BCG in my upper matted to his lower, because his is piston and mine is gas.

[Ivan275]

1. Take out the BCG and charging handle, look threw the back is the forward assist getting in the way?

2. Take out the BCG but leave the charging handle in, put it back together, can you use the charging handle ok?

3. Take out the charging handle but leave BCG in, put it back together, threw the ejection port can you move the BCG back?

4. Take out just the hammer, does it work now?

Edit:Just reread your post

I tried his upper and BCG on my lower and it worked fine. I tried my upper and BCG on his lower, and it worked fine.

That doesn't make sense unless you get creative with the problem. His buffer tube is out of alignment/bent and your BCG is narrower then his. So your narrower BCG can clear the bend of his tube and his wider BCG can not? I'm at a loss too.

[rivraton]

It definitely seems and feels like the BCG is dragging on the hammer. But, his upper doesn't do it on my lower, and my upper doesn't do it on his lower, so odd.

I couldn't try his BCG in my upper matted to his lower, because his is piston and mine is gas.

Trade uppers and call it a day....

[m3rhkp]

bring it to a gun smith

[jimbo74]

at this point, I would start swapping piece by piece and testing before you move on to the next piece

[Bullets&Whitewalls]

I came across one once that the pin on the barrel extension was missing. Have no idea where the hell it could have gone or how he over looked it. The barrel extension had come loose though making it hard for the bcg to come back. That was a rifle built with some really cheap parts.

[Bullets&Whitewalls]

Check and see if the barrel nut is loose

[gemini1]

You can try to remove/disassemble one part at a time. Take the buffer and spring off, with the rifle in a vertical position, see if the bcg, can be pulled all the way and if it will move back forward (gravity) on its own.
BTW, is there any scratch mark on the bcg or on the receiver, buffer tube end?

[wpod]

Extreme newbie to AR'S but,
Does his lower function check ok without the upper attached? (hammer move freely?)

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