It does what it's supposed to, and it'll have advantages and disadvantages over other rounds.
556.00
556 mm with stock retracted, 730 mm with stock extended.
556 rounds to 550 to the nearest tenth. However, if you want the nearest hundredth then it would be 600.
.0219 inches OR .556 mm (USG)
Probably 25 gauge, which is .556 mm thick. However, 26 gauge is close too, it is .478 mm thick.
937 rounds to 940
A 9 mm round out of a Glock 17 is 1148 feet per second
556
556 * 556 = 309,136
Depending on the depth of the round brilliant cut, the measurement can be estimated at about 8 mm at the girdle.
600
The M-16 round is a 5.56 mm round. It's smaller than an AK-47 round (7.62mm) A 5.56 mm will kill easily! Hoo-ah