SIG's SG 551-1P (SG is an abbreviation for Sturmgewehr, or assault rifle) is a gas-operated weapon designed for the demanding tactical situations that police and special units commonly encounter. The SG 551-1P is equipped with a highly tested and accurate sighting system.
The version used by the R6 team uses 3 quick change magazines, each holding 30 rounds of ammunition. Stats:  5.56x45mm NATO  900rds/min  3x30round quick change magazine