Description
The AR-15 is the most modular shooting platform in the world, and if you're looking for an easy way to swap calibers, you have to get this upper assembly. It turns your .223 or 5.56mm-firing AR into one chambered in the .300BLK caliber. And swapping calibers is fast too. Just pull out the takedown and pivot pins, remove your current .223 or 5.56mm upper, replace it with this one, and push the pins back in.
Simple.
This prebuilt upper assembly comes to you complete with a 16" stainless steel barrel accompanied by a 13.5" free float handguard. The handguard makes excellent use of the M-Lok attachment system, so you can easily mount your accessories, like foregrips, tac lights, or whatever else. You can even use your current .223 or 5.56mm mags with the .300BLK caliber. All that's left is for you to mount either backup sights or an optic of your choice.
AR 15 RIFLE KIT SPECS:
Gas System: Pistol-length
Barrel Profile: M4
Barrel Steel: 416R
Barrel Finish: Stainless
Chrome Lining: No
Muzzle Thread: 5/8×24
Chamber: .300BLK
Twist Rate: 1:8
Barrel Extension: M4
Gas Block Size: .750″
Gas Block Type: Low-profile
Muzzle Device: A2 Flash hider
Receiver Material: Forged 7075 T6
Receiver Type: M4
Handguard Type: 13.5″ lightweight M-Lok free float
Bolt Carrier Group Included: Yes
Bolt Steel: 9310 steel, magnetic particle inspected
Bolt Carrier Profile: Full-auto
Charging Handle Included: Yes
Overall Length: 24.5″
Benefits of the 16” Pistol-Length Parkerized AR 15 Upper Assembly:
- 100% legal to own and ship to your front door
- Not considered a firearm – no FFL paperwork needed!
- 4140 steel barrel and Freedom parts kit ensure sub-MOA accuracy
- Prebuilt upper with gas system removes the guesswork of rifle making


Shipping Restrictions
Shipping of various parts and/or accessories are prohibited to states and locales (ie New Jersey, California, New York, etc…) with restrictions against certain parts and/or accessories or “assault weapons” (i.e. states with high-capacity magazine restrictions, manufacturing of semi-automatic weapons, etc..). It is your responsibility to be aware of your local firearms laws before purchasing from our website or machining a firearm. We try our best to keep our shipping page current, but laws change daily
80-Lower.com only ships within the United States. Federal legislation dictates we cannot ship our products internationally.