The Diamondback DB15 Multi-Caliber is an AR-15 style semi-automatic pistol sold as a package with two uppers. The 5.56 NATO upper has a 7-inch barrel, and a separate complete 10-inch .300 Blackout upper is included, so the caliber can be changed on the same lower. Both barrels are chrome moly with black nitride finishes. The matte black pistol has a Magpul grip, an optics-ready flattop receiver, a manual safety and a 30-round capacity.

This setup suits a buyer who wants one lower for two common AR-15 pistol calibers. Range sessions can run 5.56 one day and .300 Blackout the next, and the M-LOK handguards leave room for lights or a grip. Because this is a pistol, check that the model and any accessories meet the rules where you live before ordering.

Key features

• Complete 5.56 NATO and .300 Blackout uppers included
• 7-inch 5.56 NATO and 10-inch .300 Blackout barrels
• Black nitride chrome moly barrels, free-float M-LOK handguards
• Optics-ready flattop receiver
• Manual safety, 30-round capacity

This firearm ships to the licensed FFL dealer you choose, where you complete ATF Form 4473 and pass a NICS background check before you take it home.