Both weapons were designed by Carroll Childers of the Naval Special Weapons Center. The bottom is a magazine feed mod for an 870, and the top is his full-auto "Special Operations Weapons", which uses the same 10 round magazine (some claim it is 20 rounds but I don't buy that) that his 870 mod did. I don't think either were used operationally, and I'm fairly certain that the SOW was only ever that single prototype. There is a bit more info and a couple of extra pictured
here.