Help mating upper and lower...

[Lwstarks]

I found out that the buffer tube was in one turn too many. After it was backed off, guess what, closed like it should. In fact i can slap any upper to it now. I took it to casa grande and worked like it should with both the 9mm and 5.56 uppers.

 

[792mauser]

Good to hear that it was a simple and easily fixed problem.

 

[muta4warrior]

I found out that the buffer tube was in one turn too many. After it was backed off, guess what, closed like it should. In fact i can slap any upper to it now. I took it to casa grande and worked like it should with both the 9mm and 5.56 uppers.

I called it back in March... :mrgreen:

 

[baja]

^ Yup, you did. Good Job.

 

[Cadence63[]

The offending bit is the "ears" bit at the rear of the trigger, the bit held forward by holding pressure on the trigger in the "solution" videos. Even with it held forward it contacts the forward end of the rear of the Carrier, the 1.585" to virtually 1.6" long bit of full round metal at the rear of the carrier. I don't know what carrier they're using in the videos, but I measured six of my carriers, including a Fostec (!), and none were shorter than 1.585". The ears, compressed, are (best measurement I could make) 1.577" from the rear of the opening in the lower that accepts the upper. Gonna hit the carrier every time. Either the ears must be moved forward or the full round part of the carrier has to be shortened. The trigger can't be moved, and I don't recommend grinding on the carrier. I'll call Fostec when they're open.

Two things I noticed here, someone had trouble closing after removing the carrier. Can't understand that, should definitely close without the carrier. And I was intrigued by the suggestion to pull back on the charging handle a bit when almost closed. That would move the carrier rearward and clear the ears, but the carrier is already slam against the rear of the lower at that point, and can't be moved rearward at all until properly lined up with the buffer. Which would mean the upper and lower are mated, pin would go in. I tried it anyway, no go.