Here is a concept i came up with earlier today, A "Minigun" upper reciever that can be attached to any existing AR15/M16 lower recievers. I thought it would be ideal for heavy firefight situations or just a fun range weapon for those who want the feel of somthing more exotic. As real gatling guns will never be man-portable, This concept can as its rate of fire will not be so high but may acelerate the longer it is fired. The "M16 Minigun" may operate on a form of delayed blowback combined with a "Webley-Fosbery" grooved drum underneath the bolt to rotate the barrels. It may be fed from a magazine/drum and chambered in 5.56x45mm NATO. Although it looks, It is not or no way a gatling gun but a machine gun that changes its barrels for each shot reducing overheating/erosion.