cc-settings-icon BUILD AT HOME
80% Arms sells AR-15 and .308 80% Lower Receivers, 80% Lower Jigs and other accessories which allow you to legally build a firearm at home in most states.
We utilize state of the art 5-axis CNC machines to mill all our .308 and AR-15 80 percent lower receivers to incredibly precise tolerances using premium billet aluminum.
We also offer our patented AR-15 and .308 Easy Jigs® which is the first 80% lower jig that makes it ridiculously easy for a non-machinist to finish their 80% lower in under 1 hour with no drill press required.
Products manufactured by 80% Arms carry a lifetime warranty against manufacturing defects. We will promptly replace or repair any product that we determine to be defective.

GST-9: MOD1, Pistol Frame

Frame Color
Add Full Size Grip? [Add $19.99]
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First released in November 2019, the GST-9 V1 set a precedent for the 80% frame market. It provided a modular grip system while maintaining Gen 3 G19 parts compatibility. With 3 years of customer feedback and thousands of rounds down range, we’ve raised the bar again with the new GST-9 MOD1 frame!

The gas pedal shape and location were revised and re-contoured for optimized controls during the recoil cycle. The grip system was redesigned to guarantee a flush fit with grip modules when building out your frame. Last but not least, the rear rails were split into a 2-piece system to greatly help streamline the assembly process.


  • Modular frame gives you the possibility of a 19, 19X, 19L, & 17 size weapon system in a single 4-in-1 platform.

  • Compatible with Glock 19 Gen 3 parts, holsters, & aftermarket accessories. 

  • Ergonomic: undercut trigger guard, high beavertail, glove bevel, scalloped mag release, no finger grooves, & gas pedals for your support hand as standard.

  • Premium internal rail components extended 3X OEM length, made of stainless steel.

  • Flared magwell: large built-in flared magwell ensures fast magazine changes and eliminates the need to buy expensive add-on magwells.

  • Easily ships to your door & completes in minutes.

  • Calibers: can be built out to support 9mm (G19) /.40cal (G23) /.357 Sig (G32).

 *Please Note: GST-9 MOD1 frame only accepts G19 Gen 3 compatible internal parts and slides.

**MOD1 frames are fully compatible with Glock 19, Glock 19L, & Glock 19XL slides. Glock 17 slides are not supported.

80 Percent Arms strives to provide the highest level of customer service within the 80% and firearm industry as a whole. We support all of our products with a lifetime warranty* so you can build with confidence.

Regulatory Information:

Due to ATF regulations, we cannot legally include the jig or frame rails with the MOD1 frame. The jig and MOD1 frame must be purchased on our website as two separate items. Each jig includes one set of MOD1 frame rails. You will need to purchase one jig for every MOD1 frame you plan to build. Frame rails are ONLY included with the jig, not with the 80% lower itself.

You can always expect prompt and educational information as customer satisfaction is our bread and butter. For any questions or concerns regarding our products, please contact us at either, (949) 354-2767 or message us via our live chat!

Shipping Restrictions:

This item is restricted from shipping to California, Connecticut, New Jersey, New York, Washington D.C, Washington, Hawaii, Colorado, City of Philadelphia Pennsylvania, Maryland, Illinois, and Rhode Island

 Under California law, this product is or contains an unserialized “firearm precursor part” and cannot be sold into the State of California. 80% Arms cannot accept any orders of this product for shipment to the State of California, or to any customer who is a resident of the State of California.