9mm SIG SAUER® P320 Compatible 80% Pistol Build Kit (Carry-Sized, Black) w/ Free Carry Case



Want a badass EDC pistol that transforms into different handguns? Ready to become an at-home gunsmith in the process? The SIG SAUER® P320 is the latest weapon platform where you can start building with a compatible 80% frame by using the Modular Universal Pistol 1 (MUP1) insert. This 80% Fire Control Unit serves as the guts of the P320 pistol, Sig’s latest and greatest.

The Modular Sig Sauer® P320

With their reputation for ingenuity, SIG SAUER® has done the remarkable: They created a universal firearm (the FCU) that serves as the “core” for a full line of quickly customizable, mix-n-matchable handgun configurations. Simply replace the grip module (frame), slide and barrel in a few minutes, and you can convert your EDC compact into a subcompact or even full-size handgun. The P320 is even capable of swapping calibers (9MM, .357SIG, or .40 S&W).

All you need to build your own P320 from scratch is - you guessed it, an 80% Fire Control Unit insert, and that’s where the MUP1 insert comes in.

Modular Universal Pistol 1 (MUP1) insert

The MUP1 chassis is JSD Supply's answer to your calls for an 80% Fire Control Unit insert for the P320. With the included jig and tool bits, you need only perform a few basic machining steps to make your 80% insert a functional Fire Control Unit. No experience is necessary. The included “sig jig” and tool bits come with instructions, and total machining time is less than an afternoon. Next, it’s all about the final assembly.

P320 Lower Parts & Build Kit

With the 80% insert machined, all that’s left is installing the included P320 parts kit - all the guts and internals that transform your FCU insert into a functional, ready-to-fire P320 chassis. The assembled chassis can then be completed by installing the build kit: The barrel and recoil spring assembly, slide, and grip module (frame) install onto the FCU in just a few minutes with hand tools, and you’re ready to hit the gun range. 


  • Modular Universal Pistol 1 (MUP1) insert: The basis of the P320 platform. This is the universal firearm you’ll need to finish cutting and drilling. This enables you to finish your P320 on your own without the need to go through an FFL first.
  • The Jig: Required to finish your MUP1 80% insert. The jig shows you where to drill and what to fabricate. Even first-timers can get the job done in an hour or two.
  • The Lower Parts Kit: Required to assemble the FCU, making it functional. Quality, U.S.-made.
  • The P320 Modular Build Kit: A carry-sized slide with night sights (includes barrel and guide rod/recoil spring assembly, a full-sized grip module (frame).
  • Carry case: Because why not? Protect your pristine new shooter. It’s on us.


No FFL required  Made in the USA  Lifetime Warranty

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.

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, 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.