The term Designated Marksmen Rifle has been around for a long time, but in the last 8yrs it has really made a comeback. When the United States invaded Iraq, there was more street fighting and urban engagements that in the first Persian Gulf War. I remember making some comments to a few friends about what we will see evolved with the military now that we actually have boots on the ground. We expected to see the M16 replaced by now, but according to many sources, the piston driven versions of the M16 are in service in Special Forces and some branches. Even rumors that the H&K 416 was used to kill Osama Bin Laden.
You can make any rifle into a Designated Marksmen Rifle. In my opinion it usually means putting a higher magnification optics like a Trijicon ACOG or Leupold Rifle Scopes on them. If you have a good enough operator behind a weapon the standard M16A2 can be a very leathal weapon out to 600yds, especially with the right type of ammo. There are some really good rounds for longer engagements, but the .308 is probable a better choice. There are many times where a bad guy sticks his head out and it’s too hard to get them with an M4 Carbine. The LWRC REPR is probable the nicest .308 gun designed for this role that is actually a few pounds lighter than it’s predecessors.