Real time inventory. No backorders. Ships NEXT business Day!

phone: 888-568-1771
80% Lowers & Frames Compared

80% Lowers & Frames Compared

Posted by on Sep 2nd 2022

You're ready to become an at-home gunsmith! Fabricating a custom firearm from scratch requires picking up an 80% lower or frame, officially called a "receiver blank". This guide compares available AR-type receiver blanks and 80% frames that you can buy and build. 

Types of 80% Lowers (AR Platform)

Forged AR-15 80 Lower (anodized or raw)

The forged AR-15 80% lower is the first receiver blank to hit the market years ago. It's forged from aluminum, like most retail-bought stripped lower receivers. 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 anodized 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:

  • AR-15s chambered in 5.56/.223, 300 BLK, 6.5 Grendel, and calibers that fit 5.56/.223 receivers.
  • All standard retail AR-15 lower parts and upper receivers.
  • AR-type 9mm and .22 LR conversion blocks.

Features & Specs:

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

Billet AR-15 Lower (anodized only)

The billet AR-15 80% lower is the upgraded version of the forged 80% lower. Functionally, both units are identical. This billet version is CNC-machined from 6061-T6 aluminum. Its machined construction provides some convenient upgrades, including an integrated trigger guard and threaded takedown detent and bolt catch pin holes.

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. Replacing those roll pins with threaded fittings provides an easier assembly process. This unit features a mil-spec type III hardcoat anodized finish, too. No raw version is available.

Billet AR-15 80% lowers available here.

Compatible with:

  • AR-15s chambered in 5.56/.223, 300 BLK, 6.5 Grendel, and calibers that fit 5.56/.223 receivers.
  • All standard retail AR-15 lower parts and upper receivers.
  • AR-type 9mm and .22 LR conversion blocks.

Features & Specs:

  • Made of 6061-T6 billet aluminum.
  • Type III hardcoat anodized finish.
  • Threaded fittings with integrated trigger guard.
  • The easiest AR-type lower receiver to assemble.

Billet LR-308 80% Lower (anodized or raw)

Some shooters prefer to build a rifle like the original ArmaLite AR-10, or the SR-25 from Knights Armament Company, both chambered in .308. The billet .308 80% lower provides the same form and function as those now-defunct, expensive, collectible rifles that you wouldn't otherwise be able to assemble.

The aluminum .308 variant of the AR-type 80% lower is available as a billet unit with roll pin fittings or threaded fittings, "in the raw" or with a mil-spec type III hardcoat anodized finish.

Billet .308 80% lowers available here.

Compatibility (LR-308 vs. AR-10)

It's important to note that modern .308 ARs -- including this lower receiver blank -- are not built on the ArmaLite or KAC platform. Instead, they're built off DPMS Panther Arms' LR-308 platform. Differences in the shape of the upper receivers, barrel nut threads, and other parts compatibility issues mean the LR-308 is not interchangeable with the AR-10 and SR-25. Functionally, the DPMS .308 configuration is otherwise identical to those rifles.

The .308 lower receiver blank uses mostly 5.56/.223 components in its lower parts kit, except for a few components that are sized specifically for the larger caliber. Those non-interchangeable parts include the:

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

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

Compatible with:

  • ARs chambered in .308 Winchester, 6.5 Creedmoor
  • All available. 308 AR upper receiver assemblies

Features & Specs:

  • Made of 6061-T6 billet aluminum
  • Raw or type III hardcoat anodized finish
  • Roll pin fittings available with integrated trigger guard
  • Threaded fittings available (upgraded / premium lower)
  • An affordable alternative to the AR-10, SR-25 platforms

5. Billet AR-9 80% Lower (anodized)

Pistol-caliber carbines have become popular among AR builders. Those once stuck with taking an existing AR-15 chambered in 5.56 or .223 and modifying it to shoot pistol rounds can now build a dedicated AR chambered in 9mm. 

This "AR9" receiver blank is a redesigned AR-15 lower that's been made to accept Glock magazines, 9mm upper assemblies, and one-piece bolt carrier groups designed for blowback operation without the need for the AR's conventional gas system. This lower includes a 9mm ejector and it's designed to work with 5.56/.223 lower parts kits, triggers, and buffer assemblies.

9mm 80% lowers available here.

Compatible with:

  • AR9 chambered in 9mm Parabellum
  • Works with Hybrid G-9 bolt carrier group
  • works with factory 9mm Glock magazines
  • Works with standard 5.56/.223 upper receivers
  • 5.56/.223 upper receivers now accept 9mm barrels
  • Works with 5.56/.223 lower parts kits and buffer tubes

Features & 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.

Types of 80% Pistol Frames

Polymer 80% Pistol Frame (Glock®-compatible)

The polymer 80% frame was as the built-it-yourself alternative to Glock® handguns. Like the AR-15's stripped lower receiver, the stripped frame of the Glock® is considered the firearm by law. If you're familiar with Glock handguns, you already know there are a ton of different models (currently over 50), and that continues to grow. Various Polymer80 frames can be used to build a handgun compatible with most Glock® models and their components.

80% Frame & Glock® Compatibility

Polymer80 PF940V2

Compatible with Glock® 17, 17L, 22, 24, 34, 31 (.357 SIG), 34, and G35

Polymer80 PF940SC

Compatible with Glock® 26 and G27

Polymer80 PF45

Compatible with Glock® 20 and G21SF

Polymer80 PF9SS

Compatible with Glock® 43

Polymer80 PF940C

Compatible with Glock® 19, 23 & 32

80% 1911 Frame (raw/anodized)

Stealth Arms developed the forged aluminum 80% frame for the 1911 platform, ditching the gun's original steel frame in the process. This reduces weight by more than 50%. The 1911 frame blank is compatible with standard 1911 components in .45 ACP and 9mm.

1911 Frame Compatibility

The full-size (5") 80% 1911 frame is designed to replicate the original M1911 Government's configuration. This frame blank is available in 9mm or.45 ACP with a raw finish or black hardcoat anodizing. Builders can pay a few extra bucks to pick up this frame with an under-barrel Picatinny rail for installing accessories, like a light or laser.

Features & Specs:

  • Forged and machined from 7075-T6 aluminum
  • Compatible with standard 1911 components
  • Available chambered in 9mm or .45 ACP
  • Accepts standard steel 1911 magazines

1911 80% frames available here.

Sig P320 80% Frame

Sig Sauer introduced the P320 modular handgun to replace its P250 DAO handgun. The P320 departs from Sig's usual designs and instead uses a universal "fire control unit", or FCU. The modular FCU allows owners to swap out the barrel, slide, magazine, and caliber, and even size of the pistol. The 80% market took advantage of this new fire control unit and put out a P320 "80%" version called the MUP1, shown above.

Like the stripped lower receiver for the AR-15 and stripped polymer handgun frames, the FCU is the part of the Sig P320 that's legally considered a firearm.

The P320 FCU can be swapped out for four sizes/profiles:

  • Full Size (4.7" barrel)
  • Carry (3.9" barrel)
  • Compact (3.9" barrel)
  • Subcompact (3.6" barrel)

Although they share the same barrel, the Compact P320 is shorter (5.2") than the Carry version (5.5"). 

The P320 accepts four calibers:

  • 9mm
  • .357 SIG
  • .40 S&W
  • .45 ACP

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, 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.