The Maxim PDX-SD SBR 5.56 NATO in OD Green is an integrally suppressed short-barreled rifle with a 5.5-inch barrel (Maxim part no. MXM-49100). The PDX-SD is Maxim Defense’s suppressed version of its PDX, with the suppressor built into the rifle rather than threaded onto the muzzle. This version is chambered in 5.56 NATO, feeds from a 20-round magazine and wears an OD Green finish. It is a semi-automatic rifle for shooters who want a short, quiet 5.56 in one package.

Key Specifications

• The chambering is 5.56 NATO, the standard AR-15 cartridge.
• Barrel length is 5.5 inches, which keeps the rifle very short.
• The suppressor is integral to the rifle, so there is no separate can to mount.
• Magazine capacity is 20 rounds, a compact magazine for a compact rifle.
• The action is semi-automatic, one round per trigger pull.
• The color is OD Green, a classic military shade.

Frequently Asked Questions

What color is this PDX-SD SBR? This version is OD Green, chambered in 5.56 NATO with a 5.5-inch barrel.

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 short-barreled rifles. It transfers on a Form 4473 with a background check through a Class 3 (SOT) dealer. State and local laws still apply. Taking an SBR across state lines still requires an approved ATF Form 5320.20.

Is the suppressor built in? Yes. The PDX-SD is Maxim’s integrally suppressed PDX, so the suppressor is part of the rifle.

Buy the Maxim Defense PDX-SD SBR 5.56 NATO 5.5-Inch, OD Green

As of October 9, 2026, this short-barreled rifle 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 Maxim Defense‘s silencers and suppressed firearms lineup and our Lubbock, Texas team will handle the transfer, and it ships fast to your Class 3 dealer. OD Green sets this PDX-SD apart from the Black and Arid rifles.