Welcome to Considered Outlaws, the new Leitner-Wise lifestyle brand.

We’ll be offering unique limited run products that accurately reflect the ethos behind Leitner-Wise. Everything available is conceived, designed and either produced by us, or a selected vendor in the US using North American sourced raw materials. We are not badge engineering any of the products we offer here.
In order to offer distinctive takes on product lines, we will release collaborative collections with selected partners.

Follow our social media accounts and watch for our product drops.


$2 000.00
In stock
Product Details

MARKFIVE BOOMBOX Complete Upper Receiver Assembly. Built To Order.

MARKFIVE BOOMBOX Complete Upper Assembly - 16" Cerakoted short-stroke piston upper with 12.6" MLOK Handguard.

US Patent No: 10,240,892 - Other US Patents Apply.

The 604 BOOMBOX upper receiver assembly is a novel version of the standard MARKFIVE. The short-stroke piston operating system is the result of almost two decades worth of understanding and development of these critical components. Correcting the deficiencies in the legacy operating system and later piston systems, the design, manufacture and processing has resulted in outstanding reliability, soft shooting, minimal muzzle rise, and an unparalleled consistency of performance.

Bringing together a number of patented Leitner-Wise technologies in one performance package, the BOOMBOX complete upper receiver is a reimagined concept that marries the early 604 receiver style with modern, state-of-the-art, internals. The heart of this includes the Long Advance Carrier with corrected cam path; Combat Match Bolt; Precision Cam Pin, and Titanium Firing Pin. A Cold Hammer Forged 41V45 CMV Steel 16" Combat Match Barrel, 1 in 7 right-hand six groove twist, with Nitrided finish.

Powering the system is the patented Leitner-Wise non-adjustable short-stroke piston operating system. This utilizes a one-piece, fluted, and fully supported operating rod, with true self-regulation for over-pressure. A quick-detachable gas block, for disassembly if required. All heat, pressure and friction surfaces are nitrided then hard chrome plated for durability and adverse environmental condition capability. The operating system is tuned and timed correctly allowing the use of a carbine buffer and spring which minimizes reciprocating mass for smoother operation.

The BOOMBOX 604 Upper Receiver is forged from 7075 aluminum with the period correct "carry handle", no shell case deflector, polymer ejection port cover, and M4 feed ramps. The 12.6" handguard is machined from aircraft grade, heat-treated, extruded aluminum and designed to provide optimum cooling and airflow for the barrel, light weight, and high strength. A ambidextrous Raptor LT charging handle is utilized and all BOOMBOX uppers are supplied with installed period correct rear sight, lightweight aluminum A frame removable front sight, BOOMBOX carbine buffer and spring, and a Leitner-Wise Heavy Duty Buffer Retainer.

  • MARKFIVE OPERATING SYSTEM - Patented Short-Stroke Piston System.
  • BOLT CARRIER GROUP - Full Combat Match Components.
  • BOOMBOX 604 UPPER RECEIVER - Polymer No Forward Assist. M4 feed ramps.
  • MARKFIVE HANDGUARD - Patented 12.6", MLOK, Lightweight QD Handguard.
  • COMBAT MATCH BARREL - Cold Hammer Forged, 1-7" Twist, 6 Groove, 5.56 NATO.
  • MUZZLE DEVICE - A1 or 3 Prong Flash Hider.
  • CHARGING HANDLE - Ambi Raptor LT.
  • BOOMBOX BUFFER AND SPRING - Carbine Weight, Heavy Duty Buffer Retainer.
  • SIGHTS - 604 Front And Rear.
  • COLOR - Armor Black. FDE And Sniper Grey Available On Request.
  • BUILT TO ORDER - Please allow 14-28 for delivery depending on specification.
Save this product for later