Spartan.. you are right. The M4 is the current standard issue weapon for most US combat forces plus a lot of swat teams and other military organizations also use the M4... unless you're a marine, then you get second-hand army gear

Here is a more tricked out M4 with the M203 grenade launcher.



a bit of trivia that most people don't know.. the buttstock of the M4 extends out - I don't think I've ever seen an M4 model with the buttstock extended and both the M4 and M16 fire single round and 3 round bursts... both can be made fully auto but generally they are never issued that way since it's a wast of bullets.