So.... is the lower compatible with other AR uppers? The mag well compatible with standard Mags? What’s to prevent a change?
Don’t know with these, on most AR platforms, they are (except for the very early ones where the latching pin sizes are different). But as I intended to say, I think the posted picture is NOT of their new prototypes, it looks like a picture of a couple of 223/556 M-4 clones.