TacFire's BU-556-5 is a complete AR-platform upper assembly with a 5-inch 5.56 NATO barrel finished in black nitride, a black anodized 6061-T6 aluminum receiver and an M-LOK handguard. The barrel is 4150 CMV steel, and the whole upper weighs 1.9 pounds. It is sold as a drop-on assembly for an existing lower, with receiver, barrel and handguard already fitted.

This is the shortest practical format for an AR pistol lower, and a Texas owner picks it to build a compact 5.56 for the home or the truck that still runs the same magazines as a full-size rifle. The nitride barrel and anodized receiver resist corrosion, and the M-LOK slots take a light and a hand stop. Pair it with a buffer and gas setup suited to a barrel this short, and test it on the range before trusting it.

Key features

• 5.56 NATO complete upper, 5-inch black nitride barrel
• 4150 CMV steel barrel
• Black anodized 6061-T6 aluminum receiver
• M-LOK handguard
• 1.9 pounds

Upper assemblies are parts and ship straight to your door in Texas, no dealer transfer needed.