The LWRC ICMKII 12.7-inch Patriot Brown SBR is a 5.56 NATO short-barreled rifle built around LWRCI’s patented short-stroke gas piston system (LWRC part no. ICMKIIR5PBC12S). LWRCI forges the Monoforge one-piece upper for added strength over a standard-pattern upper, and coins every forging for precise dimensions and a clean surface finish. A Black Nitride treated, cold hammer forged barrel with a 1:7 twist handles a wide range of 5.56 bullet weights. Fully ambidextrous lower controls, LWRCI Skirmish back-up iron sights and an A5 two-position gas block round out the design. The Patriot Brown finish gives it a look of its own among short piston rifles.

Key Specifications

• The chambering is 5.56 NATO, a standard carbine cartridge.
• Barrel length is 12.7 inches, the mid-length ICMKII short-barrel option.
• The barrel is cold hammer forged with a 1:7 twist and Black Nitride treated for wear and corrosion resistance.
• The operating system is LWRCI’s patented short-stroke gas piston, which keeps carbon out of the receiver.
• The upper is a Monoforge one-piece, coined forging with an integrated rail base.
• It is equipped with an A5 two-position gas block for suppressed or unsuppressed operation.
• It ships with a 30-round Magpul PMAG, a full-capacity AR-pattern magazine.

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 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.

What finish does this ICMKII have? It is finished in Patriot Brown, one of the five colors LWRCI offers on the ICMKII alongside black, flat dark earth, tungsten grey and OD green.

Are the controls ambidextrous? Yes. The bolt catch and release, magazine release and safety selector are all fully ambidextrous.

Buy the LWRC ICMKII SBR, 5.56 NATO, 12.7-Inch Barrel, Patriot Brown

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 LWRC‘s semi-auto rifles lineup and our Lubbock, Texas team will handle the transfer, and it ships fast to your Class 3 dealer.