Real time inventory. Ships next business day!

phone: 888-568-1771
80% Lower Compatibility Guide

80% Lower Compatibility Guide

Posted by 80-Lower.com on Nov 17th 2022

You're ready to become an at-home gunsmith and build an AR-15 from scratch. But which receiver blank should you buy? 

This guide compares available AR-type 80% lowers, which calibers they work with, and other specifications you'll need to know before building.

New here? Read "What is An 80% Lower?"

Need to find the right lower parts kit? Read this LPK compatibility guide.

Types of 80% Lowers

Forged AR-15 80% Lower

The forged AR-15 80% lower is the first receiver blank to hit the market years ago. It's forged from 7075-T6 aluminum, like the typical retail-bought AR stripped lowers. It's the most affordable AR receiver blank that isn't made of polymer. The raw (non-anodized) version is the cheaper of the two, allowing you to apply a custom coating once fabricated. 

The black version is coated with a type III hardcoat anodized finish (mil-spec), so it'll match any retail AR-15 parts, upper, or built kit you pair it with. Although not fabricated nor functional, the forged AR 80% lower incorporates a finished, threaded buffer tube housing, front pivot and rear takedown pin holes, a machined magazine catch channel, and trigger guard mounts.

Forged AR-15 80% lowers available here.

Compatible with

Available Calibers

  • 5.56 NATO, .223 Remington
  • 300 AAC Blackout
  • 6.5 Grendel
  • All other calibers compatible with 5.56/.223 lowers

Quick Specs

  • Made of 7075-T6 forged aluminum.
  • Raw or type III hardcoat anodized finish.
  • The most affordable aluminum AR-type 80% lower.

Read the AR-15 Build Guide here.


Billet AR-15 80% Lower

The billet AR-15 80% lower is an upgraded version of the forged lower. Both units function identically. The billet receiver is CNC-machined from 6061-T6 aluminum. It includes some upgrades, including an integrated trigger guard and threaded takedown detent and bolt catch pin holes. These threads make assembly simpler, since no roll pin punches are required.

Roll pins can be difficult to install or remove, and they require special punches, If you've assembled a lower receiver before, you know what we're talking about. This lower is also treated with a mil-spec type III hardcoat anodized finish. No raw version is currently available.

Billet AR-15 80% lowers available here.

Compatible with

Available Calibers

  • 5.56 NATO, .223 Remington
  • 300 AAC Blackout
  • 6.5 Grendel
  • All other calibers compatible with 5.56/.223 lowers

Quick Specs

  • Made of 6061-T6 billet aluminum.
  • Type III hardcoat anodized finish.
  • Provides easier assembly w/ LPK.

Billet LR-308 ("AR-10") 80% Lower

The aluminum .308-type 80% lower is the modern version of the military's AR-10 receiver. It's available as a billet unit machined with roll pin fittings or threaded fittings. It's also available in "in the raw" (uncoated) or with black type III anodizing.

Billet .308 80% lowers available here.

Compatibility: LR-308 vs. AR-10

Modern .308 ARs (including this receiver blank) are not based on the original ArmaLite AR-10. Instead, they're based on DPMS Panther Arms' LR-308 rifle. The LR-308's receivers are shaped a bit differently than the AR-10's receivers, and the upper receivers' barrels are also different. Otherwise, the DPMS .308 AR is functionally identical to the AR-10.

This lower uses mostly 5.56/.223 components in its lower parts kit, except for a few parts that are sized specifically for the larger caliber. The only parts not used from the AR-15's lower parts kit include the:

  • Buffer
  • Bolt catch
  • Pistol grip
  • Takedown pins
  • Magazine catch

AR-10 vs. LR-308: What's Different?

Compatible with

Quick Specs

  • Made of 6061-T6 and 7075-T6 aluminum.
  • Raw or type III hardcoat anodized finish.
  • Roll pin fittings (7075) or threaded fittings (6061) available.

5. Billet AR-9 80% Lower

Pistol-caliber carbines have become popular among AR builders. Instead of modifying your 5.56/.223 lower with a 9mm conversion block, you can now build a dedicated AR chambered in 9mm with this lower. 

This AR9 receiver blank is a redesigned AR-15 lower with a modified magazine catch and magazine well that accept Glock magazines. It has a built-in 9mm ejector, designed to work with the 9mm bolt carrier group found in AR9 upper assemblies. It uses a standard AR-15 lower parts kit, including the same trigger, hammer, disconnector, safety, and springs. The same is true for AR-15 buffer assemblies. The 9mm only requires a heavier buffer.

9mm 80% lowers available here.

Compatible with:

Quick Specs:

  • Made from 6061-T6 billet aluminum.
  • Type III hardcoat anodized finish.
  • Factory-installed 9mm ejector.
  • Factory-installed magazine catch.
  • Integrated trigger guard.
  • Uses standard takedown pins.

Read the AR-9 Pistol Build Guide here.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At 80-lower.com, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.


We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.