Building a Custom 8.6 Blackout AR-15 Upper Receiver

Introducing the 8.6 Blackout

The 8.6 Blackout is an innovative new cartridge design intended for use in AR-15 style rifles. It offers ballistics similar to the venerable .30-30 Winchester in a compact package built to harness the ergonomics and modularity of America's most popular rifle platform.

Background of the 8.6 Blackout

The idea behind the 8.6 Blackout was to create an efficient and hard-hitting round for the AR platform that could rival traditional brush guns and lever actions. Various wildcatters had experimented with short, fat .30 caliber rounds in AR-15s, but the 8.6 Blackout took the concept and refined it even further.

Advanced Armament Corporation and Lehigh Defense collaborated to design the 8.6 Blackout and market loaded ammunition, brass, dies, and other components to support it. The round was quickly adopted by hunters and competitive shooters alike.

Cartridge Specifications

The 8.6 Blackout fires a .308 caliber bullet in a shortened .300 AAC Blackout case. Overall length is kept to 2.260 inches to feed reliably in standard AR-15 magazines. Unlike wildcat cartridges, the 8.6 Blackout is SAAMI approved and pressure rated for 42,000 PSI.

The Upper Receiver

The foundation of any AR-15 build is the upper receiver, consisting of the barrel, bolt and bolt carrier group, handguard, gas system, and charging handle assembly. Constructing an 8.6 Blackout upper requires the same process as a standard AR, with considerations for the unique cartridge specifications.

Barrel Options

The 8.6 Blackout was designed around barrels with a 1:6 twist rate, which will stabilize bullets up to 250 grains effectively. Most major barrel manufacturers now offer 8.6 Blackout barrels in lengths ranging from 10.5 to 24 inches. A 16 or 18 inch stainless barrel with lightweight profile is a good all purpose choice.

Bolt Considerations

Stock AR-15 bolt assemblies can be used with the 8.6 Blackout provided the barrel has a .300 Blackout style feed ramp. However, an enhanced bolt is recommended for optimal function. The bolt should be of good quality tool steel and machined appropriately for the larger .30 caliber cartridge.

Gas System Length

Mid-length or rifle-length gas systems are common on 16+ inch 8.6 Blackout barrels. The extra dwell time allows reliable function with heavier bullets compared to carbine length setups. Adjustable gas blocks may be useful for optimizing function with various loads.

Muting Sound with Suppressors

The 8.6 Blackout plays very nicely with sound suppressors due to the efficient short powder burn. The subsonic loads in particular were designed with suppression in mind. Most AR-style muzzle devices and quick attach suppressor mounts will interface perfectly with an 8.6 Blackout barrel.

Customizing and Accessorizing Your Build

One of the great aspects of the AR platform is mixing and matching components to create your ideal setup. The only limit is your imagination! When outfitting an 8.6 Blackout upper, stock up on quality magazines and sights/optics suited for the heavier projectiles and brushed hunting ranges this cartridge shines at.

Chassis and Handguard Choices

Free float M-LOK compatible handguards in the 15-20 inch range allow mounting accessories without contacting the barrel. Chassis systems like the AG Composites REAPER give you an adjustable, modular stock and grip built for stability and comfort over extended range sessions.

Trigger Enhancements

A quality drop-in trigger like those offered by Geissele Automatics or CMC Triggers will greatly improve the feel and consistency of your rifle. Take up that gritty factory trigger creep and stack with a smooth, crisp aftermarket unit.

Upgraded Bolt Catch and Mag Release

Enhanced controls from Battle Arms Development and others upgrade the aesthetics and ergonomics of your rifle. Choose from various shapes, textures, and finishes to perfectly match your build.

The 8.6 Blackout upper from any reputable parts supplier will serve as the foundation for a superb hunting, tactical, or competitive shooting rifle. Let your shooting ambitions guide the accessories and customizations! Before long, you'll have a highly personalized blackout tack driver bringing home trophies from the range or the woods.

FAQs

What barrels are recommended for the 8.6 Blackout?

Most manufacturers offer barrels from 10.5 to 24 inches with a 1:6 twist rate to stabilize up to 250 grain bullets. A 16-18 inch stainless barrel with lightweight profile balances versatility and performance.

Can I use a standard AR-15 bolt with the 8.6 Blackout?

A standard bolt will work if the barrel has an appropriately sized .300 Blackout feed ramp. However, an enhanced bolt made of quality steel is recommended for optimal durability and function.

What gas system length should I use?

A mid-length or rifle-length gas system allows reliable function and softer recoil compared to carbine length. This is especially helpful when shooting heavier subsonic loads.

What muzzle device or suppressor mount is ideal?

Most AR-15 30 cal muzzle devices and quick attach suppressor mounts will properly fit an 8.6 Blackout barrel. This versatility makes adding a sound suppressor hassle-free.