80% P320 Compatible Insert - MUP 1

(20 customer reviews)




Building a firearm in your garage is easy with help from JSD Supply. We offer a diverse inventory of parts, like 80% lower inserts, that make a great base for a variety of handgun projects.

The Modular Universal Pistol 1, or MUP 1, is compatible with current P320 upgraded parts, including SIG’s line of “drop safe” firearms. You can use this insert to make a 9mm, 40 S&W, 357 SIG, and 45acp (with slight modifications). That means this SIG P320 insert is extremely versatile. Design a SIG P250, a P320, or even put it in the EXO-1 Chassis system.

This quality insert is made from type 316 stainless steel, so it will last you through years of use.

Roughly 2 weeks for shipping

Easy to Build Firearms

Since 2013, we’ve been the ultimate DIY firearm solution. With this insert, you have a base from which to build your new favorite firearm in the privacy of your own garage. To finish the insert, you need the following:

  • All Holes
  • Bend Slide Rails
  • Trim Rails to Size

You can easily complete all of the operations on your SIG P320 insert with a Dremel, Drill Press and our MUP-1 Jig (sold separately). Follow instructions to complete a gun that looks, feels, and operates just like one from the manufacturer but without the hassle of paperwork.

The Hassle-free Way to Get a Handgun

Whether you need an 80% lower insert or something else for your firearm project, rely on JSD Supply. Our team has tested everything we sell and are happy to make recommendations so you can complete your build. Offering straightforward services and fast shipping, we are the hassle-free way to get a handgun without background checks or concerns about serial numbers.

Additional information

Safety Option


20 reviews for 80% P320 Compatible Insert – MUP 1

  1. ROBERT B (verified owner)

    Surprisingly simple. Was hesitant because I have no machining experience. This plus the finishing jig and video (and patience) made a success!

  2. tim (verified owner)

    Fast shipping insert looks great will buy more very soon!

  3. Steven Speidel (verified owner)

    A+++++ Excellent craftsmanship! Very helpful customer service and fast shipping! JSD answered a question I had within minutes . Thank You!!

  4. [email protected] (verified owner)

    Fits good , easy to work .
    Either it or jig need markings for manual safety cutout .

  5. [email protected] (verified owner)

    Fits good , easy to work .
    Either it or jig need markings for manual safety cutout .

  6. Arthur Borger (verified owner)

    I have now finished two of these inserts using your jig. It has been a pleasure working with your products. Everything worked perfectly. I would recommend some good cobalt drill bits for this project as the insert is very hard to drill.

  7. Carter Sturm (verified owner)

    The first and second amendment are under attack in this country, and the MUP-1 is a genuine contribution to protecting the 2nd. I can’t tell you how great it felt to complete my P320. Thank you JSD Supply!

  8. Anonymous (verified owner)

    Great product, only problem I had was drilling the #39 holes (same as the first one I did). It seems the material is hardened at this point. However I found out that reducing the drill rpm to 1200-1500helped greatly.

  9. Eugene (verified owner)

    Will be getting another mup1 insert in the future for another build. This was a little bit more challenging than I had initially thought, but a very satisfying project for a home garage tinkerer/hobbyist. Go slow, follow the instructions, and reach out to JSD if you have any questions, this is a super responsive vendor with top notch customer support.

  10. Joe (verified owner)

    Item arrived and was as described. Shipping was very quick, faster than some other companies offering similar products. I received immediate follow up for my order, and an update when it shipped with tracking info. The insert itself looks great. A few manufacturing marks that are merely cosmetic and will not have an impact on function. This was my first order with JSD Supply, an I must say I am thoroughly impressed. I will definitely order from them again.

    Thank you,

  11. Joshua Smith (verified owner)

    Exactly what I ordered. Fast shipping too, Thanks.

  12. Alex Mack

    Finished mine this beautiful morning of the 4th of July, with their jig and a dremel this was a very straight forward fun rewarding build! Didn’t take me long assembling FCU with JSD’s parts, upon completion slide went on with ease and first mag ran flawlessly! Ran 165 rounds through so far today and this trigger is as good if not better than my factory X full. I’m so happy with how this build turned out, would 1776% recommend to anyone wanting a fun project with an awesome outcome!

  13. mike (verified owner)

    thank jsd supply, The P320 Compatible Insert was great and looked perfect. We will be ordering two more of these in the future.

  14. mike (verified owner)

    thank jsd for shipping fast just 10 day after im order the items is great will oder again

  15. Mike (verified owner)

    Nice stuff shipping was super fast only once week come to my house thanks jsd

  16. Mike (verified owner)

    Thanks jsd only one week stuff come to my house love jsd

  17. Mike (verified owner)

    Thanks jsd only one week stuff come to my house

  18. David (verified owner)

    Fantastic pieces! Better than Sig due to them being stainless. The jig is of amazing quality, not link a cheap jig you’d get for an ar build. I also don’t think you’d be able to complete this without a jig.

  19. Eric (verified owner)

    Took my time drilling, deburring and dry-fitting my parts and pins. (PATMOS KIT) I went out to fire this weekend and it ate everything I fed it-even steel cased! Slow and steady, make yourself an awesome pistol!

  20. Shawn (verified owner)

    Great product! This has been the best 80% experience I’ve ever had! Was looking for more of a challenge compared to p80’s and this did not disappoint. So grateful JSD made this Product, so we can once again enjoy our freedom. Just bought another today without manual safety this time! I recommend everyone try one!

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