SIG P320 Series Part 2 Build Resources ***update 3/10/21

Updated: Jul 6

Contribution from Kevin Wilhelm (aka Tohopka) & Photo ashere814

I've put together a comprehensive list of the parts you'll need to build your Sig Sauer P320 FCU's You'll notice that the complete lower parts kits are listed at the bottom. The reason being... locating a complete lower parts kit right now is damn near impossible and has been that way for quite some time.

If you have the time and patience... you might even have to set up alert notifications on your phone (when emails are sent from vendors letting you know parts are back in stock) but over the course of the last month, I have been able procure 95% of the required parts to build (3) full FCU's, so it can be done vs waiting another year for complete lower parts kit to become available.

If you received an email notification.... jump on it right away! Don't be surprised if you're only 15 minutes late to the party and the stock has already been depleted... there really is that much Demand right now for these parts!! When Marine Gun Builder begins his video tutorial series of the P320 FCU build, I imagine the parts situation is only going to get worse with the increased demand.

I'm hoping/have my fingers crossed that when I post this info that the format doesn't become a jumbled mess... it would be nice if we could edit posts, but I don't see where there is an option to do so.

In any event, I hope some of you find this useful.

**Note: When ordering MUP-1's or the required jig, check JSD Supply's website first and use "MGB" discount code to get free shipping. I've listed other sites where JSD Supplies MUP-1 and Jig can be purchased if JSD Supply themselves are currently out of stock.

MUP-1 "Without" Manual Safety

The link above defaults to an MUP-1 without manual safety, but at the bottom, there's an option to check the block for a MUP-1 WITH manual safety

MUP-1 "WITH" Manual Safety

Abprototype will modify MUP-1 for a manual safety, but at $55 for the modification, you'd probably be better off waiting for one to become available. However, this would be a good option for someone who has an MUP-1 without manual safety and doesn't want to buy another/modified the MUP-1 they have in hand.

**Note either of the above MUP-1's listed above can be built as a 45 ACP with a minor modification.

JSD Supply's Jig

FCU Parts List

Pin, Slide Catch lever

Pin, Safety Lever

Pin, Trigger Stop

Pin, Split coil

Lever, Take Down Safety

Spring, Takedown Lever

Trigger Trigger Bar

Spring, Trigger Bar

Sear Housing Assembly:

Sear Housing


Pin, Sear Pivot Pin

Springs, Sear (2)

Safety Lever

Spring, Safety Lever

Disconnector, Trigger Bar

Slide catch assembly:

Slide Catch

Slide Catch Spring

Spring Post,Slide Catch Lever

Video Link:

Sig Sauer's comparison of the P320's pre and post upgrade. It's a short, informative video produced by Sig to explain the differences of the pre and post voluntary upgrade for the drop trigger issue. This will also help you to verify whether or not you received pre, or post upgrade parts when ordered.

Sources to purchase "Sear Group Assembly" instead of having to search and procure parts individually.

Midwest Gun Works

Sig Sauer

Sear Group Assembly (INCLUDES Sear Pivot Pin) PN: 8900033

Sig Sauer P320 Sear Housing (Black Oxide) PN: 1301974-03-R

Alternate Choice with a DLC finish:

Sig Sauer P320 Sear Housing, (DLC Finish) PN: 1301974-02-R

Sear w/ Secondary Striker Notch, New Style, PN: 1302192-R

Safety Lever PN:1300739-R

Safety Lever, Captive (M17) PN: 1302387-R

This captive safety lever is manufactured for the P320 (Civillian version of the Military M17

Sear Springs PN: 1300799-R Qty (2)

Safety Lever Spring PN: 1300673-R

There's much discussion on the internet as to whether or not this part is still needed post upgrade... The P320 actually functions the same with, or without the spring installed. It's my understanding that Sig Sauer no longer installs the safety lever spring after performing drop trigger upgrade. There's plenty of information on the internet on the subject for you to read and make your own decision.

Sear Pivot Pin PN:1301060-R

Safety Disconnect

PN: 1302031-R

Slide Catch Assembly Kit, 9mm, 40 S&W, and 357 Sig PN: KIT-320-SCL Hyperlink:

Description: Sig Sauer P320 Slide Catch Assembly KIT 9MM, 40 S&W and 357 Sig. This parts kit includes a black steel slide catch lever, slide catch lever spring and slide catch lever spring post.

If purchased individually:

Slide Catch Lever PN: 1301763-R

Slide Catch Lever Spring Post PN: 1300876-R Slide

Catch Lever Spring PN: 1300246-R Hyperlink:

Upgrade Slide Catch Levers:

Sig Sauer P320 Slide Catch Lever, Tungsten (DLC finish) PN: 1301763-02-R Hyperlink:

Wilson Combat Sig Sauer P320 EXTENDED Slide Release, Black. Hyperlink: