I just finished my build with the MAG tactical lower and here is my impression. Although the lower is lightweight (magnesium). It has a painted coating that does not wear like cerakote. In some of the spots where clearance matters the most it fails. I got it to work but with some fitting required.

Pivot and take down holes were very tight. The mag button hole was machined the exact size of the button. It required tons of material to be removed. And the threads for the buffer tube left a burr and it prevented the upper from closing all the way.

This is what I received in a trade and i wanted to use it. But if I were to do it again, I would throw it in the trash.