The CMMG DEFCAN 556 5.56mm suppressor is a full-auto rated rifle can built from Inconel for heat tolerance under sustained fire (brand part no. 55CA42D). This version is the direct-thread configuration, and it ships with a 1/2×28 muzzle brake. CMMG builds the DEFCAN-556 body on the industry-standard 1.375×24 HUB interface, so the mount can be changed later to suit a different host or QD system. The suppressor body weighs 8.8 ounces without its mount, and the sealed design keeps cleaning simple. It is a durable 5.56 can for a carbine or short-barreled AR that gets run hard.

Key Specifications

• The caliber is 5.56x45mm, the cartridge CMMG designed the DEFCAN-556 around.
• Construction is Inconel, a nickel alloy chosen for strength at high temperature.
• It is full-auto rated, per CMMG’s firing schedule.
• Minimum barrel length is 6.5 inches for 5.56mm, so it works on short AR barrels.
• The body is 1.375×24 HUB threaded, for swapping to other HUB mounts.
• This version is the direct-thread configuration and includes a 1/2×28 muzzle brake.
• Body weight is 8.8 ounces without the mount, and the body diameter is 1.54 inches.
• The finish is black Cerakote, a hard coating over the Inconel body.
• It is a sealed design, so routine cleaning does not involve pulling a front cap or baffles.
• It is made in the USA and backed by CMMG’s Lifetime Quality Guarantee.

Frequently Asked Questions

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.

What is the shortest barrel it can be used on? CMMG lists a 6.5-inch minimum barrel length for 5.56mm with the DEFCAN-556, and rates it for full-auto use.

Can I change how it mounts? Yes. The body uses the industry-standard 1.375×24 HUB interface, so the mount can be replaced with another HUB direct-thread or QD mount.

Buy the CMMG DEFCAN 556 5.56mm Suppressor, Direct Thread, Black

An Inconel can rated for full-auto and 6.5-inch barrels has the durability margin a hard-used carbine needs. 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 CMMG‘s silencers and suppressed firearms lineup and our Lubbock, Texas team will handle the transfer, and it ships fast to your Class 3 dealer.