80% P320 Compatible Insert – MUP


(19 customer reviews)

Out of stock

Want to be notified when this product is back in stock?

Categories: , SKU: MUP1


The new 80% Sig Fire Control Unit (Modular Universal Pistol or MUP), 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.
With this insert, you have a base from which to build your new favorite firearm. 
To finish the insert, you need to complete the following:
Drill All Holes
Bend Slide Rails
Trim Rails to Size
Complete all of the operations on your MUP insert with a drill press jig (sold separately).
DISCLAIMER: We do not provide legal advice or legal counsel. It is your responsibility to understand the respective State laws and Federal laws. This product is to be installed by a competent gunsmith. No liability is expressed or implied for damage or injury which may result from installation or use of this product. These inserts require milling and possibly fitment of the various parts included. We do not provide build and/or gunsmithing advice.

Due to the legal nature of these inserts, we do not accept returns or exchanges on these frame kits for any reason.

We cannot ship these to the state of New York, New Jersey, Delaware, Illinois, California, Washington or Maryland.

19 reviews for 80% P320 Compatible Insert – MUP

  1. Daniel O’Dell

    Fit right.

  2. joe

    what a deal, great price, i have ordered a few things from rocky brass, and they never disappoint on shipping. they are by far the fastest turn around out of any company out there. will be ordering again.

  3. Mr.

    If you do your part right, take your time and use a quality drill press and cobalt bits, not the bits that come with the jig, deburr the sharp edges and polish the rails, you’ll be rewarded with a better than stock FCU.

  4. siggy

    These unfinished blanks are very well done. The tolerance between the jig and the blank are spot on with no play. The steel is strong so you won’t be to worried about bending the blank out of shape. I would recommend this project for anyone that thinks the PF80’s are to simple, yet not ready for the 1911.

  5. Andrew Labanon

    Solid insert take your time prepping and drilling do not rush! Polish all deburred holes and your mup is good to go!

  6. Rob

    First time ordering from Rocky Brass and couldn’t have been happier with the service, price and shipping. Definitely recommended and will be ordering form again!

  7. Bruce

    Such a great way to build your own P320. Perfect fit. I recommend this.

  8. Steve

    Fit is exact. Incredibly fast shipping. Gret customer support

  9. Mark

    With some TLC the MUP can be turned into a P320 FCU that works just as well as a factory part. I will say I have a mill and press. I’m not sure how someone with a Black and Decker home user drill and a file would fare. The safety slot could be a real challenge. I took my time, especially with the rails, and the fit was perfect. Worth the time and $ invested.

  10. Zachary Elliott

    Rockey Brass is my first stop for Sig builds. Timely deliveries, quality products and responsive staff. Easily one of the best in the biz.

  11. Doug

    I can’t remember ever ordering this and I kind of hope you all forget it as well… Thank you.

  12. James Bishop

    Only place that had the 320 lowers in stock and shipping was super fast. To my door in 3 days. Thanks

  13. Philip Casey

    I ordered this when it was put on sale. I had been thinking about it for some time now. Looking forward to starting on it. Just need to get a jig! With the political situation and goose-stepping Dems in charge, that may never happen.

  14. Jon

    Received the MUP-1 very quickly from Rockey Brass. Very good service from Rockey Brass. Now I need to get the unobtainable jig so I can do something with it.

  15. Bill

    Worked great no issues at all. thank you Rockey Brass

  16. Steve

    The MUP is is well made but easily bends out of shape if you try hammering your pins in when you install your parts. Make sure the sizes of the bits. The bits which came with my jig bought here were all but one too small for the pins that came with a quality lower parts kit bought elsewhere. You must do a lot of filing to take the sharp edges off so the upper will slide easily. Do that and make sure the holes for the pins are the proper size and the lower will be exactly what you need for a proper firearm.

  17. Scott Feller

    Works great top quality fast shipping couldn’t be any better

  18. Peter J. Bertini

    Nice kit. Happy I made the purchase

  19. Alejandro Macari

    Excellent product, well made, easy to use, delivered on time, I’m going to order some more …

Add a review

Your email address will not be published.

Post comment