Now this sounds just too cool!
Safir Arms .410 AR-15 Upper With Mag [D10L1] No Rifling smooth bore Hunting barrel, Used for Semi-auto only comes with one 5rd mag .410 Caliber, Works best with Winchester or Federal 2 3/4 shells, Made In Turkey $579.99
Check it out!.They have got other great gear also, for reasonable prices. I am not compensated or affiliated with Cope's. Just a happy customer!
Add this to your collection of uppers (6.8, 9mm, etc...) for the AR family. I am willing to bet that a 20 or 30 round mag can be modded for use also. Nothing like a potential 15+ rnd .410 mag loaded up with slugs and buckshot to ruin someones or somethings day!