Well, I went and put my youngest boy's upper on the poly lower. The takedown pin/hole alignment was........... ok. I finally got it tgether and decided to do a quick dry function test to see if the charging handle could at least get the BCG to go back and forth in the buffer tube.
Nope, no such luck. Meh, oh well. I need to be more careful next time putting the buffer tube on. I'm still not completely sure the threads weren't off; considering how the rest of it fit together.
No need for further "testing" out at the range or with ammo,because it would never even get that far. I may wait and see if they get their QC squared away before buying any more of these. I took the lpk out and it will be waiting for an aluminum lower.
Which reminds me..... Next project is an 80% aluminum lower with a jig. This may wait for another month or two, though.