The M16A4 may soon retire. This week, the Marine Corps announced via internal memo that the M4 carbine will become the primary-issued rifle in infantry and security units, as well as replace the M16 rifle in supporting training schools by September 2016. Commandant of the Marine Corps Gen. Robert Neller approved the change, which was first proposed to the previous commandant, Gen. Robert Dunford, according to Marine Corps Times. This decision falls in line with the Army’s phased transition away from the M16 over the past few years. The M16A4 is on the outs simply because it is outdated, and here’s why: