In the AR world, swapping to a 5.5'' 300 blackout pistol barrel or fitting a 5 inch complete upper assembly brings big gains without a full rebuild. These options from Moriarti Armaments let you tailor your rifle to tight spaces, quiet shooting, or fast, out-of-the-box use.
A 5.5'' 300 blackout pistol barrel measures just 5.5 inches, keeping your overall length compact and legal under pistol rules. This barrel turns your lower into a personal defense weapon you can maneuver easily in vehicles, hallways, or crowded ranges. Special rifling and chamber dimensions stabilize both fast supersonic rounds and heavy subsonic loads, delivering reliable accuracy out to 150 yards. Threaded 5/8×24, the 5.5'' 300 blackout pistol barrel accepts flash hiders, brakes, or direct-thread suppressors with a simple twist. Built from 4150 CMV steel and finished with a hard nitride coat, it resists heat, wear, and heavy use for years of dependable service.
For those who want a ready-to-go solution, the 5 inch complete upper assembly is ideal. Each 5 inch complete upper ships fully assembled, head-spaced, and test-fired, so you only need to attach it to a Mil-Spec lower and you’re ready to shoot. Its mid-length gas system softens recoil and reduces component wear, even during rapid-fire drills. A nitride-treated 7075-T6 aluminum receiver mated to a cold-hammer-forged barrel provides tight tolerances and sub-MOA potential with match-grade ammo. The free-float handguard spans the barrel length and offers full-length M-LOK slots for lights, grips, or bipods without touching the bore. An ambidextrous charging handle and dust-cover-compatible design make this upper comfortable for both right- and left-handed shooters.
Combining a 5.5'' 300 blackout pistol barrel with a 5 inch complete upper gives you ultimate flexibility. Use a dedicated pistol build one day and swap to a carbine-length setup the next, all on the same lower receiver. You save money and bench time while enjoying consistent performance whether you run suppressed subsonic ammo or high-velocity supersonic loads. The quick-change nature of these components lets you adapt to different missions—close-quarters defense, home protection, or backyard plinking—with minimal effort.
If you’re ready to move beyond one-size-fits-all ARs, choose Moriarti Armaments precision parts. Our 5.5'' 300 blackout pistol barrels and 5 inch complete upper assemblies deliver reliable accuracy, low recoil, and rock-solid durability in a simple, modular package. Visit our website today to configure your build, explore accessories, and place your order. Elevate your AR platform now and feel the difference of custom-grade components.