Yep. I agree that M4 is lighter and has a lot of thing to do with it. Since I'm a " Thai Reserve Officer Training Corps Student " or TROTCS (mostly made of 15-18 years old boys) It's hard to get a hand on a up-to-date firearms. We usually train with non-functional M1Garands or Carbines . But there are several guns like HK33, M4s and Tar21 in the Army and they're still using M16s.