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



Ready to take your pistol building experience to the next level? Sig Sauer® got into the DIY game some time ago with the ultra-modular P320. We’ve caught on, and now you can build arguably the coolest handgun in the Sig line from scratch with compatible parts. The 80% compatible Sig Sauer® P320 build kit is now in stock and ready to build, jig and tooling included.

Sig Sauer® P320 Modularity

Sig Sauer® did something genius with their P320 line: They built an entire line of full-size, compact, and subcompact handguns into one modular weapon platform. Swap out the grip module, slide and barrel, even caliber (9MM, .357SIG, and .40 S&W available). The only part of the platform considered a firearm is the P320 Fire Control Unit -- and that’s where the MUP1 insert comes in.

Modular Universal Pistol 1 (MUP1) insert

Just like  the 80% lower receiver for the AR-15, we’re excited to offer the MUP1 insert for the Sig P320. This is JSD Supply's great answer to your calls for an 80% Fire Control Unit insert. With the included jig, tool bits and instructions, all it takes is an afternoon with a few hand tools to fabricate your own, functional FCU.

P320 Lower Parts & Build Kit

With the 80% insert drilled and fabricated, final assembly of the FCU means installing the included P320 lower parts kit. Once installed, you’ll be the proud owner of a modular, ready-to-fire Sig Sauer® P320! To get you off the workbench and onto the firing line, we also included a full-size 9MM P320 build kit:

  • 9mm Full Size Complete Slide
  • Full Size Medium Grip Module
  • Barrel & Recoil Spring Assembly
  • Night sights
  • Carrying case


The platform that fits 9MM parts will also accept .357 SIG and .40-S&W P320 parts.


  • Modular Universal Pistol 1 (MUP1) insert: The basis of your P320 platform. This is the Fire Control Unit you’ll need to fabricate with the included jig. This process enables you to finish your P320 on your own without the need to go through an FFL.
  • The Jig:  Required to finish your MUP1 80% insert. It takes away the guesswork by showing you where to drill and what to fabricate. No experience necessary.
  • The lower parts kit:  Required to assemble your FCU into a ready-to-fire insert.
  • The P320 “exoskeleton”:  A full-size slide with night sights (includes barrel and guide rod/recoil spring assembly) , a full-sized grip module (frame).
  • Carrying Case:  A simple, convenient carrying case to protect your newly minted P320.


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.