AR15 doubling/won't hold zero

[Gatehouse]

One of my AR15's went weird today. The Leupold scope was out of zero, and adjustment to zero it was erratic. Weird.I thought the scope might be pooched.

So I was was trying to zero it and it started doubling! Not every time, but often.

Suspecting a sticky firing pin, I put in a new BCG. Same thing.

So I suspected something was up with the lower internals....but then I noticed the front takedown pin was working itself loose, the detent wasn't doing it's job. It was getting later in the day, so I have yet to examine it closely, but I suspect a sloppy connection between upper and lower has caused both problems, with the scope bouncing around shot to shot, and the trigger disconnect not fully engaging

Damn, life was so much simpler when I only focused on bolt actions...

 

[zuke]

Live and learn!

 

[rkm456]

An accuwedge may help to take up some of that slop. Another option are KNS takedown pins:

 

[barsik]

the only time I had doubling was when my hammer pin broke. part of the pin still held the hammer at an angle, but the disco couldn't pick up the notch. a genuine wtf moment.

 

[Hilo71]

Check the disconnector. if there is part of a primer or debris in/ under there it could double