The Spike's Tactical STU5435MLS is a complete AR-15 upper receiver assembly in 5.56 NATO, built around a 16-inch midlength barrel and ready to drop onto your lower receiver right out of the box. Spike's handles the heavy lifting—every upper is inspected, tested, and function-fired at their facility before it ships, so you get a battle-ready assembly without the guesswork. Whether you're building a reliable patrol rifle, a range workhorse, or a defensive carbine, this upper delivers the core you need to finish the job.

The receiver is forged from 7075-T6 aluminum, the same material spec Spike's uses in their complete rifle builds. That means you're getting tolerances and build quality that meet their own high standard. The 16-inch midlength barrel is cold-hammer-forged (CHF) and phosphate-coated for durability and corrosion resistance—a proven combination for reliability and longevity in the field. The A2 front sight base is pinned in place, giving you a solid foundation for backup iron sights or co-witnessing with an optic mounted further back on the receiver.

The 12-inch SAR3 handguard gives you plenty of rail real estate for lights, lasers, and tactical accessories without adding excessive weight or length. Paired with the complete M16-profile bolt carrier group included in this assembly, you've got all the internal components you need for reliable function. This is not a stripped upper—it arrives as a functional unit, ready to mate with your lower and run. If you're assembling a 5.56 carbine and want to skip the parts sourcing and assembly work while keeping quality high, this Spike's upper takes one major step off your plate.

The Spike's Tactical STU5435MLS is a complete AR-15 upper receiver assembly in 5.56 NATO, built around a 16-inch midlength barrel and ready to drop onto your lower receiver right out of the box. Spike's handles the heavy lifting—every upper is inspected, tested, and function-fired at their facility before it ships, so you get a battle-ready assembly without the guesswork. Whether you're building a reliable patrol rifle, a range workhorse, or a defensive carbine, this upper delivers the core you need to finish the job.

The receiver is forged from 7075-T6 aluminum, the same material spec Spike's uses in their complete rifle builds. That means you're getting tolerances and build quality that meet their own high standard. The 16-inch midlength barrel is cold-hammer-forged (CHF) and phosphate-coated for durability and corrosion resistance—a proven combination for reliability and longevity in the field. The A2 front sight base is pinned in place, giving you a solid foundation for backup iron sights or co-witnessing with an optic mounted further back on the receiver.

The 12-inch SAR3 handguard gives you plenty of rail real estate for lights, lasers, and tactical accessories without adding excessive weight or length. Paired with the complete M16-profile bolt carrier group included in this assembly, you've got all the internal components you need for reliable function. This is not a stripped upper—it arrives as a functional unit, ready to mate with your lower and run. If you're assembling a 5.56 carbine and want to skip the parts sourcing and assembly work while keeping quality high, this Spike's upper takes one major step off your plate.