Help me build a P365

September 01, 2026, 05:03 PM

I am wanting to build a mission specific P365 to run with a JK 105CCX suppressor. I've been away from the P365 ecosystem for a while and need some help putting together a build.
The goal is a XL 12 round grip module with a 3.1" slide and threaded barrel to attach a can.

I think I will use the Mirzon grip module: https://mirzon.com/products/hy...e-for-sig-sauer-p365
It's a bit larger than the standard XL grip from front to back, which suits my larger hand size

I will need a good slide and internals, I'd like something with good serrations/ grip, but not overly Gucci, and I need a good threaded barrel to go with it.

The biggest question is a FCU. I know I could buy one from SIG, but I'd like to find one that has a better trigger. Maybe a Legon FCU?
This will be a carry gun, so I don't want extended controls and a 2lbs. trigger pull.

Any direction towards trusted sources would be greatly appreciated.

And if you've built your own, lets see it!

September 01, 2026, 07:34 PM

RogueJSK

quote:
Originally posted by Nick:
The biggest question is a FCU. I know I could buy one from SIG, but I'd like to find one that has a better trigger.

With my latest P365 build, I found it was significantly cheaper to buy a complete P365 then sell off everything but the FCU, compared to buying just a FCU. Doing it that way the FCU cost me a total of $170 when the dust settled, rather than the ~$350 to buy a FCU alone. I then installed an aftermarket trigger, grip module, slide, and barrel.

In your case, I would recommend going the economical route by simply buying a complete P365X and keeping the factory slide, mags, and FCU. Then install an aftermarket trigger in the factory FCU and a threaded barrel in the factory slide, and stick all that on your Mirzon grip. Finally, sell your factory barrel and grip module, or just toss them in your parts bin.

The unfortunate truth is that to buy a standalone FCU and a decent aftermarket slide, plus the parts to finish the stripped slide, would run you ~$750 just for those pieces alone. Compared to paying $500 for a complete factory P365X and just keeping the factory slide, FCU, and mags. You could then finish out your build with a $100 threaded barrel and a $100 better aftermarket trigger and still come out paying ~$50 less for your totally completed build (with 2 extra mags) than it would cost you to buy just the standalone FCU and aftermarket slide alone.

September 01, 2026, 07:50 PM

RogueJSK

Here's my latest build:

-Sig factory FCU (minus the trigger)
-Tyrant CNC trigger (or Grayguns also has a great P365 trigger)
-Wilson Combat XMacro grip module
-Shalotek EDC XL slide
-Shalotek XL barrel
-Sig factory slide internals kit and recoil spring
-Angry Bear Arms blacked out sights

Plus a Holosun SCS Carry and a TLR-7 Sub HL-X light.

And the only reason why it made sense for me to build it this way is because I not only bought and sold a factory P365 to get a $170 FCU, but I also got the aftermarket Shalotek slide and barrel combo for $175 as part of a crazy deal. Normally just the stripped Shalotek slide and barrel alone would have run me $480, effectively the same price as a complete factory gun just for the stripped slide and barrel.

So normally the math just doesn't make sense for total aftermarket P365 builds on standalone FCUs. It's easy to end up with a $1200+ aftermarket P365 build that isn't really any better than a $700 complete factory P365 with some aftermarket accessories added.

September 02, 2026, 04:58 AM

Dorian

quote:
Originally posted by Nick:

The goal is a XL 12 round grip module with a 3.1" slide and threaded barrel to attach a can.

I think I will use the Mirzon grip module: https://mirzon.com/products/hy...e-for-sig-sauer-p365
It's a bit larger than the standard XL grip from front to back, which suits my larger hand size

If I'm reading this right the grip module you linked is for an XL sized slide with a 3.7" Barrel, not a p356/p356X slide of 3.1.

From Mirzon site, (Compatibility:- P365 XL and X-Macro Slide length)

September 02, 2026, 07:08 AM

RogueJSK

Perhaps he means this one, which can be used with a 3.1 slide and XL 12 round mags:

https://mirzon.com/products/x-...e-for-sig-sauer-p365

September 02, 2026, 07:51 AM

Nick

quote:
Originally posted by RogueJSK:
Perhaps he means this one, which can be used with a 3.1 slide and XL 12 round mags:

https://mirzon.com/products/x-...e-for-sig-sauer-p365

Yes, that is the one I meant to post.

September 02, 2026, 07:56 AM

Nick

quote:
Originally posted by RogueJSK:
quote:
Originally posted by Nick:
The biggest question is a FCU. I know I could buy one from SIG, but I'd like to find one that has a better trigger.

With my latest P365 build, I found it was significantly cheaper to buy a complete P365 then sell off everything but the FCU, compared to buying just a FCU. Doing it that way the FCU cost me a total of $170 when the dust settled, rather than the ~$350 to buy a FCU alone. I then installed an aftermarket trigger, grip module, slide, and barrel.

In your case, I would recommend going the economical route by simply buying a complete P365X and keeping the factory slide, mags, and FCU. Then install an aftermarket trigger in the factory FCU and a threaded barrel in the factory slide, and stick all that on your Mirzon grip. Finally, sell your factory barrel and grip module, or just toss them in your parts bin.

The unfortunate truth is that to buy a standalone FCU and a decent aftermarket slide, plus the parts to finish the stripped slide, would run you ~$750 just for those pieces alone. Compared to paying $500 for a complete factory P365X and just keeping the factory slide, FCU, and mags. You could then finish out your build with a $100 threaded barrel and a $100 better aftermarket trigger and still come out paying ~$50 less for your totally completed build (with 2 extra mags) than it would cost you to buy just the standalone FCU and aftermarket slide alone.

Thank you for taking the time to post your thoughts. After doing some cursory investigation and reading the comments, it looks like a donor gun is the better play.