JSD Supply MUP-1 Frame

JSD Supply

$99.00 - $209.00
(14 reviews) Write a Review
Calculated at Checkout
Build Difficulty:


This is the current production JSD Supply 80% MUP-1 frame to build yourself a custom or self-built pistol based on the SIG Sauer P320. It will work with any P320 9mm, 40SW or 357SIG (not manual safety without modification). Will also work with 45ACP with minor modifications. Current production frames fit the new drop parts. Please note these are the current production frames offered by JSD. Frames require JSD Supply MUP-1 jig for completion. (Add a discounted jig above).

Frame requires finishing to be a complete firearm. All city, state and Federal laws apply when manufacturing your own firearm. Engraving is available for an additional fee. Engraving info can be found HERE (or checkbox option)

Includes: 1 JSD Supply MUP-1 (SIG P320) Unfinished Frame (Manual safety cut available for +$55) (Discounted jig available for +$110).

Manual safety version of the MUP-1 can be found here: MS JSD MUP-1

FCU Parts, Barrel, Slide, etc. are obviously NOT INCLUDED. SHIPPING RESTRICTIONS APPLY TO CA, CT, DC, IL, MD, NJ, NY, WA.

No FFL is REQUIRED. THIS IS NOT A FIREARM. 80% frames cannot be returned. JSD has their ATF determination letter stating this is not a firearm.

See our option to add the manual safety pocket to your existing frame: Manual Safety Cut

14 Reviews Hide Reviews Show Reviews

  • 5
    Sig P320 build

    Posted by D Shawver on Aug 18th 2022

    This is my first attempt at the Sig frame build, so I will circle back to review the actual product, but I have no doubt it will be as good as every other MUP-1 frame. This is also my first order with AB Prototype and that is what gets the 5 stars here! Always nervous with first order experiences but AB Prototype has been an excellent first experience, so much so I've placed more orders already and will be placing more. Ordering was a seamless process, shipped reasonably quick and arrived on time as promised, wouldn't ask for anything more. Thank you AB Prototype!

  • 5
    Mup-1 frame

    Posted by Michael on Jun 27th 2022

    Excellent quality. Excellent fit in module . Have had 0 failures since completed insert has been installed. Very happy with this product. I would definitely buy again . I would definitely recommend this product to others. The customer service was awesome. All technical questions were answered promptly and accurately by knowledgeable staff . Very satisfied overall.

  • 2
    The item was bad but service was great

    Posted by Unknown on Feb 26th 2022

    Abprototype has great service definitely 5 stars. However this is a product review and I’m disappointed. I felt like I was doing 80% of the work. Had to smoothed out a lot of the top surface. Although I didn’t drill with a drill press, I had enough experience to drill, but on the bigger holes it took me 3 set of drill bits. If they pre-drilled the holes then I would agreed that it was 80% completed. Anyway if I had I choice I would just spend 350 on the fcu.

  • 5
    JSD Supply MUP-1 Frame

    Posted by Spence on Aug 23rd 2021

    I've built every P320 There is from Full Size 9mm to .40 S&W Sub-Compact. This is the best 80% Gun on the market in my opinion. I've built every Polymer80 Glock they have so far, All AR's (AR-9/10/15/.40&.45acp). I'm a mechanic by trade but no one will ever take my build's no matter what! Over my dead body Biden Prick! Protest to Survive!!!

  • 5

    Posted by Chris on Aug 19th 2021

    Fast delivery, excellent part, very simple process will definitely be ordering my future build parts from AB Prototype

  • 5
    well made unit

    Posted by Ralph Koon on May 31st 2021

    very professionally made

  • 5

    Posted by Barrett Grubb on Jan 27th 2021

    Excellent frame and jig.....Not hard for someone with medium gunsmithing experience to complete with their jig and instruction videos...these sigs are a bit pricey to build in comparison with glocks but in the end the trigger capability on the sig is much better and I guess you get what you pay for to an extent....overall happy with the purchase and shipping was amazingly quick during a time when a lot of places are late getting stuff out.

  • 4

    Posted by Marc Silberberg on Jul 9th 2020

    Broke two bits on the #39, but was all around easy to do.

  • 5
    Sig mup

    Posted by Oswaldo Herrera on Feb 22nd 2020

    Well made.