The Dead Air Sierra 5 KeyMo is the KeyMo-mount version of Dead Air’s dedicated 5.56 suppressor (Dead Air part no. SIERRA5KM). Dead Air offers the Sierra 5 out of the box with either its KeyMo or Xeno mounting system, and this one carries KeyMo. Welded Cobalt 6 baffles sit inside a stainless outer tube, and the knurled exterior is function over form. The body is 4.87 inches long and 10.8 ounces without an adapter, and it is full-auto rated with no barrel length restrictions. It makes sense for shooters who already run KeyMo muzzle devices on their rifles.

Key Specifications

• The mount is KeyMo, Dead Air’s quick-detach system for rifles fitted with KeyMo devices.
• Rear threads are 1.375-24 HUB, so the Sierra 5 can be reconfigured with other HUB adapters.
• The caliber rating is 5.56 NATO and .224 Valkyrie, per Dead Air.
• The energy rating is 2200 ft-lbs, Dead Air’s published figure for this model.
• Bore diameter is 5.56mm, matching the dedicated 5.56 design.
• Length without an adapter is 4.87 inches, compact on a carbine.
• Weight without an adapter is 10.8 ounces, light for a stainless can.
• Diameter is 1.5 inches, a tube size that keeps the rifle balanced.
• Materials are Cobalt 6 baffles and a stainless steel tube, chosen for long service life.
• The finish is black Cerakote, a durable coating that resists wear and glare.

Frequently Asked Questions

Which mount does this Sierra 5 use? This version comes with the KeyMo mounting system out of the box. Dead Air also sells a Xeno version, and both use HUB-compatible 1.375-24 adapters.

Is the Sierra 5 full-auto rated? Yes. Dead Air lists it as full-auto rated with no barrel restrictions, and rates it for 5.56 NATO and .224 Valkyrie.

Do I need ATF approval to buy this? No. As of October 9, 2026, ATF no longer requires Form 4 approval, registration or a tax stamp for suppressors. It transfers on a Form 4473 with a background check through a Class 3 (SOT) dealer. State and local laws still apply.

Buy the Dead Air Sierra 5 5.56mm Suppressor, KeyMo Mount, Black

As of October 9, 2026, this suppressor transfers on a Form 4473 with a background check at your Class 3 (SOT) dealer, with no Form 4 or tax stamp; state and local laws still apply. Order through Dead Air‘s silencers and suppressed firearms lineup and our Lubbock, Texas team will handle the transfer, and it ships fast to your Class 3 dealer. If your rifles already wear KeyMo muzzle devices, this Sierra 5 drops right into the system you have.