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  • Sig Sauer® P320 Lower Parts Kit - 9mm/.40/.357

    Sig Sauer® P320™ Lower Parts Kit - 9mm/.40/.357

    If you're doing a Sig Sauer® P320™ compatible build, you'll need a lower parts kit to get your MUP-1 up and running. That's the part legally considered the firearm and also the part you keep when you're changing out frames, slides, etc., to...

    $149.99
  • 80-p320-compatible-insert-by-jsd-supply-1 80-p320-compatible-insert-by-jsd-supply-2 80-p320-compatible-insert-by-jsd-supply-3 80-p320-compatible-insert-by-jsd-supply-4

    80% P320 Compatible Insert

    The P320 by Sig Sauer® was a great addition to our industry. It introduced the idea that you could have one pistol, but that you could modify it to be adaptable to any carry situation. They did it by defining the insert or the "guts" of the P320 as...

    $99.99
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 Ready to build your own Sig P320 at home? Start here.

The Sig Sauer P320's modular design is all thanks to the internal chassis that holds all the fire control parts: The trigger, striker, safety mechanisms, pins and springs. Thanks to the 80% market, you can now invest in a MUP-1 chassis (an unfinished P320 chassis) and pair it with a factory-spec P320 lower parts kit. Both units are found right here.

How Does the 80% P320 Work?

First, you'll need to fabricate the MUP-1 chassis, like you would any other 80% lower receiver for a handgun or rifle. This requires cutting and drilling with hand tools. Once fabricated, you must assemble the chassis using the multi-caliber parts kit. Together, the assembled chassis is now ready to accept any of the P320's modular components: A grip module, barrel, slide, and magazine which can all be found here.

Read the Sig P320 Build Guide to learn more!

What's Included With the P320 Parts Kit

The P320 "lower", or chassis parts kit includes the internal components necessary to install all those external pieces we just mentioned above. Those internal components include:

  • Lightweight Adverse Trigger
  • Sear Housing
  • Sear
  • Safety Lever
  • Trigger Bar
  • Takedown Safety Lever
  • Takedown Lever with O-Ring
  • Mechanical Disconnector
  • Trigger Bar Spring
  • Sear Spring X2
  • Takedown Safety Lever Spring
  • Sear Housing Pin
  • Trigger Bar Stop Pin
  • Sear Pin
  • Slide Catch Lever Pin
  • Safety Lever Pivot Pin

Your build awaits.


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.

DISCLAIMER: “Sig Sauer” is a federally registered trademark of Sig Sauer, Inc. and is one of many trademarks owned by Sig Sauer, Inc. Neither 80% Lowers, a/k/a Tactical Gear Heads, LLC nor this site are affiliated in any manner with, or otherwise endorsed by, Sig Sauer, Inc. The use of “Sig Sauer” on this page is merely to advertise the sale of Sig Sauer pistols, parts, or components. For additional genuine Sig Sauer, Inc. products and parts visit www.sigsauer.com.

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.