Quote
That being said I cannot imagine an epoxied lego lower would hold up well. An AR-15 lower isn't a pressure bearing part but you're going to have a fun time keeping the rear take-down pin through-hole from snapping off with just legos and epoxy 
Legos, yes. However, this:
http://www.infowars.com/3d-printed-lower-receiver-withstands-more-than-650-rounds-gun-grabbers-panic/
Honestly I'd rather build a
