Complex sentence: The C12A1 fires a 7.62 mm x 51 mm round, the same as the round used in the Heckler & Koch G3 and the FN C1A1.
Split into simpler sentences: The C12A1 fires a 7.62 mm x 51 mm round. The 7.62mm x 51mm round is the same as the round used in the Heckler & Koch G3 and the FN C1A1.