Complex sentence: The first weapons used were the Sterling submachine gun and the L1A1 SLR; now the American M4 rifle and the Heckler and Koch UMP submachine gun are employed for duty.
Split into simpler sentences: The first weapons used were the Sterling submachine gun and the L1A1 SLR. Now the American M4 rifle and the Heckler and Koch UMP submachine gun is employed for duty.