diamondback db-15. The Diamondback DB15 CCMLB 5.56mm Rifle is made entirely in the USA! Starting with the tried-and-true, U.S. Military-proven gas-im ement system and using only the highest quality components machined in Diamondback’s CNC facility. The DB15 raises the ar when it comes to features and performance when compared to others. Diamondback DB15 represents value and versatility all at a very affordable price.