Popular Mechanics - Three Rifles That Could Replace the Army's M4A1 Carbine ... or not Or is it a new season and therefore time to re-hash. Three Rifles That Could Replace the Army's M4A1 Carbine My gut says no. Just because something is about 60 doesn't' mean you toss it away If you need an 800 m rifle, use the existing stock of M14s. What do our NATO allies use in 7.62x51 ? FAL's ? Soon enough robots will take the field and something else will be called for. Of course this ultimately comes down to a caliber argument. Garand proposed something about 7mm - the first M1s were not in 30-06. That was a Army requirement due to surplus WW1 stocks. Stoner proposed something about 7mm - the 5.56 was an Air Force (McNamera? ) change. Anyways - 6mm, 6.5, 7, 7.5 or 8 anyone? I think 7.5+ were due to limitations in power from the start of the 20th century.