After a fair amount of research, we've compiled what we think is a comprehensive look at the Mk18 rifle. From the origins of the rifle as the CQBR, a short barreled upper with the SOPMOD BLOCK II project, to a complete rifle produced and refined by Naval Surface Warfare Center - Crane, we detail the development, refinement, and construction of the rifle. We also claimed that you can modify a rifle from the base configuration and still call it a Mk18. As the photos show, the end users can and do re-equip their rifles as they see fit.
Hopefully the article is both educational and entertaining.
A Look at the Mk18 by Airsoft Outlet NW