WHAT DOES COLT SMG UPPER MEAN?

The Barrel is another budget option from Foxtrot Mike, and it is 16 inches extended. Extended to get a 9mm, but a rifle is usually a rifle and I would like that 16-inch barrel to make it so. The Foxtrot Mike barrels are remarkably straightforward. The modified close assortment aperture (50 meters) with the Colt 9mm SMG is engaged. Here is the norm