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 https://jsdsupply.com/80-p320-compatible-insert-mup-1/
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:
Pin, Sear Pivot Pin
Springs, Sear (2)
Spring, Safety Lever
Disconnector, Trigger Bar
Slide catch assembly:
Slide Catch Spring
Spring Post,Slide Catch Lever
Video Link: https://youtu.be/u9vIY2EoJwE
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 https://www.midwestgunworks.com/page/mgwi/prod/8900033
Sear Group Assembly (INCLUDES Sear Pivot Pin) PN: 8900033 https://www.midwestgunworks.com/page/mgwi/prod/8900033
Sig Sauer P320 Sear Housing (Black Oxide) PN: 1301974-03-R https://osagecountyguns.com/sig-sauer-1301974-03-r.html
Alternate Choice with a DLC finish:
Sig Sauer P320 Sear Housing, (DLC Finish) PN: 1301974-02-R https://www.midwestgunworks.com/page/mgwi/prod/1301974-02-r
Sear w/ Secondary Striker Notch, New Style, PN: 1302192-R https://www.midwestgunworks.com/page/mgwi/prod/1302192-r
Safety Lever PN:1300739-R https://www.midwestgunworks.com/page/mgwi/prod/1300739-R
Safety Lever, Captive (M17) PN: 1302387-R https://www.midwestgunworks.com/page/mgwi/prod/1302387-r
This captive safety lever is manufactured for the P320 (Civillian version of the Military M17
Sear Springs PN: 1300799-R Qty (2) https://www.midwestgunworks.com/page/mgwi/prod/1300799-R
Safety Lever Spring PN: 1300673-R https://www.midwestgunworks.com/page/mgwi/prod/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 https://www.midwestgunworks.com/page/mgwi/prod/1301060-r
Slide Catch Assembly Kit, 9mm, 40 S&W, and 357 Sig PN: KIT-320-SCL Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/kit-320-scl
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 https://www.midwestgunworks.com/sig-sauer-p320/slide-catch-levers.html
Slide Catch Lever Spring Post PN: 1300876-R https://www.midwestgunworks.com/page/mgwi/prod/1300876-R Slide
Catch Lever Spring PN: 1300246-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300246-R
Upgrade Slide Catch Levers:
Sig Sauer P320 Slide Catch Lever, Tungsten (DLC finish) PN: 1301763-02-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301763-02-r
Wilson Combat Sig Sauer P320 EXTENDED Slide Release, Black. Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/wc-320-sr
This extended slide release from Wilson Combat is constructed of high quality steel for the Sig Sauer P320 pistol. The release will fit all generations of Sig P320 firearms that are chambered in either 9mm, 40 S&W or 357 SIG. The exposed ears of the release are larger and extend further than the low-profile, hard to reach, stock option. This extended style gives the shooter greater control and grip when operating the firearm.
Slide Catch Assembly Kit for 45 ACP PN: KIT-320-SCL-45 https://www.sigsauer.com/sig-sauer-small-parts-shoppers/p320-parts-picker/?location=slidecatchlever
Slide Catch Lever Pin PN: 1300429-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300429-R
Sig Sauer P320 Trigger Stop Pin PN: 1300827-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300827-R
Sig Sauer P320 Sear / Safety Lever Housing Pin, 2.5mm x 20mm
PN: 1301341-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301341-r
Safety Lever Pivot Pin PN: 1300674-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300674-R
Takedown Safety Lever, Shortened Pin PN: 1302166-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1302166-r
(For Sig Sauer P320 pistols chambered in 9mm, 40 S&W, 357 SIG only/Not for 45 ACP.)
Takedown Safety Lever For 45 ACP
Only fits P320 models in 45ACP (manual safety or non-manual safety versions). Will not function properly for 9mm, 40SW or 357SIG pistols.
PN: STSL45-BLK Hyperlink: https://www.smallgunparts.com/Sig-P320-45-Takedown-Safety-Lever
Flat Trigger, Black Oxide PN: 1301272-14-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301272-14-r
Alternate triggers choices: Hyperlink: https://www.midwestgunworks.com/sig-sauer-p320/triggers.html
Trigger Bar PN: 1300675-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300675-R
Trigger Bar Spring, Zinc Phosphate PN: 1301575-01-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301575-01-r
Trigger Bar Spring (NO Finish) PN: 1301575-00-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301575-00-r
Manual Safety (For Sig Sauer P320 pistols chambered in 9mm, 40 S&W, 357 SIG and 45 ACP.) Trigger Bar (Manual Safety) PN: 1301357-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301357-r
Manual Safety Lever, Right PN: 1300917-01-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300917-01-r
Manual Safety Lever, Left PN: 1300916-R Hyperlink:https://www.midwestgunworks.com/page/mgwi/prod/1300916-r
Manual Safety Detent PN: 1300939-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1300939-r
Manual Safety Detent Spring PN: 1301283-R Hyperlink: https://www.midwestgunworks.com/page/mgwi/prod/1301283-r
SIG P320 OEM Lower Part Kits Small GunParts: https://www.smallgunparts.com/
Military Discount: https://www.smallgunparts.com/Military-LEO-Discount_ep_43-1.html
Factory Sig P320 9mm/40 S&W/357 Sig/Lower Parts Kit - Complete OEM
LPK Part Number: S32LPK-BLK Hyperlink: https://www.smallgunparts.com/Sig-P320-Lower-Parts-Kit
This complete lower parts kit includes all the upgraded pieces from Sigs' voluntary drop-safe recall. This kit is completely compatible with any upgraded Sig P320 slide in 9/40/357. This kit will not work with the .45 ACP Sig P320 or a .45 80% build as there are a few pieces that are different.
Factory Sig P320 9mm/40 S&W/357 Sig/Lower Parts Kit - Complete OEM LPK (With SIG Flat Trigger) Part Number: SFLLPK-BLK Hyperlink: https://www.smallgunparts.com/Sig-P320-Flat-Trigger-Lower-Parts-Kit
Sig X-Series compatible Lower Parts Kit with OEM Flat Trigger to upgrade your Sig Sauer P320 or finish your 80% Sig P320 compatible gun frame insert (MUP-1). This upgraded complete lower parts kit includes all the upgraded pieces from Sigs' voluntary drop-safe recall. This kit is compatible with upgraded Sig P320 full/carry/compact slide in 9/40/357. This kit will NOT work with the .45 ACP Sig P320 or a .45 80% build as there are a few pieces that are different, it will also not work with the subcompact model P320.
Factory Sig P320 45 ACP Lower Parts Kit - Complete OEM LPK Part Number: S45LPK-BLK Hyperlink: https://www.smallgunparts.com/Sig-P320-45-Lower-Parts-Kit
One of the few sites/vendors that actually allows you to upgrade their Sig P320 OEM Lower Parts Kit with Apex flat trigger and trigger bar for $78 (if you choose to do so) and they also have a wait list.
Factory Sig P320 M17 Lower Parts Kit - Complete OEM LPK (Manual Safety) Part Number: S32MLP-BLK Hyperlink: https://www.smallgunparts.com/Sig-P320-Manual-Safety-Lower-Parts-Kit
Lower Parts Kit to upgrade your Sig Sauer P320 M17 or finish your 80% Sig M17 compatible gun frame insert (MUP-1). This complete lower parts kit includes all the upgraded pieces from Sigs' voluntary drop-safe recall along with all manual safety components. This kit works with any upgraded Sig M17 slide in 9mm.
In my humble opinion, probably the best bang for your buck (no pun intended) when it comes to trigger upgrade systems for the P320
Grayguns Competition Trigger $149 https://grayguns.com/product/p320-adjustable-straight-trigger-system-competition/
Military/LEO/First Responder Discount Form: https://grayguns.com/discount/
Straight trigger with built in over-travel adjustment
Precision-ground custom sear, polished and finished in hard nickel PTFE. Competition Sear Springs
Intermediate competition sear springs
Competition trigger bar spring
New snappy-reset trigger bar spring
Micro-polished, extended safety lever pin