Best Upgrades for the Sig Sauer P365 [Ultimate Build]

A ripple effect was created when Sig Sauer released the P365 in 2019.

Every other gun company rushed to try and catch up to the double-stack pistol.

But why was the gun so successful?

Sig P365 SAS in straw
Sig P365 SAS

Well, first and foremost, it checked all the necessary boxes.

Reliable, accurate, ergonomic, and it generally did the basics very well.

What set the P365 apart from every other handguns, though, was its impressive capacity. Sig squeezed 10 rounds into a gun that was no bigger than guns that held 6 or 7 rounds.

Sig Sauer P365
So little but so mighty.

Success and riches fell upon Sig, and the aftermarket opened up significantly.

I’ve since taken full control of that aftermarket and built what I consider to be the ultimate Sig P365. And I want to share my upgrades with you.

So, tag along as I walk you through my build goal and all the extras it took to achieve it.

Table of Contents


Build Goal

If you need a refresher on the Sig Sauer P365, check out our video below or hop on over to our full review here.

Sig’s revolutionary P365 is a carry gun. As a carry gun, the primary use comes down to defense.

With that in mind, I upgraded the pistol to make it a better defensive gun.

This means recognizing and addressing the flaws the P365 has.

Most innovative CCW gun [2018]
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

As a small gun, it tends to be snappy with good self-defense ammo. The sight radius is rather short, and it can be tough to use beyond 15-yards with speed.

I wanted to tame the gun a bit, make it easier to shoot at various ranges, increase my follow-up shot time, and of course, make the gun look cool!

Looking cool is half the battle, right?

So Cool

Best Sig Sauer P365 Upgrades & Parts

1. Sig Sauer FCU + XL Slide

Sig invented a modular fire control unit for the original P250, which later went to the P320, and now the same idea lies within the P365.

The legal “firearm” portion of the gun is a removable chassis system that can insert into various frames known as the Fire Control Unit.

The FCU is compatible between various frame sizes and P365 models. I’ve taken full advantage of that with my P365.

Sig Sauer P365 Upgrades Trigger
Sig’s FCU

The modular design appeals to me, and I like having one firearm morph into multiple uses depending on the level of concealment or control I require.

The FCU is the core of the build, and it allows me to swap between various configurations.

My main configuration is a standard P365 frame with the XL slide. I find this an awesome combination that allows for an easy shooting gun that’s highly concealable.

Sig Sauer P365 Upgrades
It’s like Legos…but for adults.

The shorter frame disappears in an AIWB or IWB carry holster.

The longer slide and barrel increase sight radius, velocity, and control. With the two combined, I have a very effective but concealable gun.

Should I want to emphasize concealability above all else, all I need to do is swap the XL slide for a standard slide, remove some accessories and go with the shortest magazine.

at Sig Sauer Parts

Prices accurate at time of writing

Prices accurate at time of writing

2. True Precision Threaded Barrel

I knew I wanted to add a muzzle device to my P365; to do so, I needed a threaded barrel.

True Precision produced the best-threaded barrel on the market.  The ½ x 28 threads make it easy to attach a suppressor or muzzle device, so it was an instant sell for me.

Beyond just being a threaded barrel, the True Precision design accommodated a proprietary broach cut that enhances accuracy, and it is quite noticeable.

Sig Sauer P365 Upgrades
Threaded barrels mean fun accessories!

My groups tightened slightly after adding the True Precision barrel.

Beyond the broach cut, the barrel fits a good bit tighter, and that also helps in the accuracy department.

Another selling point was that the barrel could use the cheapest, crappiest ammo on the market and function perfectly fine, which is great in the current ammo drought.

3. Griffin Arms Micro Carry Compensator

Comps on carry guns are a fun subject to discuss. I like them, and since this is my build, a compensator was a piece of it.

Since this is a small carry gun, I went with a small compensator.

But which one?

The Griffin Arms Micro Carry Comp — the perfect choice.

Sig Sauer P365 Upgrades Comp
Look at that comp…work of beauty.

It’s hardly any bigger than a thread protector but offers ports to dissuade recoil and tame your gun.

“You don’t need a comp on a 9mm!” Naysayers shout.

Need is a strong word. But I agree, I don’t need it. However, I won’t deny its effectiveness.

The Griffin Arms Micro Carry Comp reduces muzzle rise and makes my subcompact pistol quite controllable and much easier to handle.

Seeing my red dot barely move between shots is a satisfying feeling. Best of all, it makes my follow-up shots faster and with greater precision.

Sig Sauer P365 Upgrades Disassembled
Sig Sauer P365 disassembled

The real work is done when you fire the gun one-handed. That was the moment I realized how handy a compensator could be.

Shooting one-handed could be a very real situation in which I could find myself.

So, being able to do so with greater effectiveness makes the Griffin Micro Carry Comp a worthwhile addition to my P365.

The Griffin Armament comp works with most P365 holsters with an open bottom design.

Most compensators are on the large side and require holsters specifically made for compensated guns. So it’s nice that the Griffin Armament doesn’t require that.

at Optics Planet

Prices accurate at time of writing

Prices accurate at time of writing

4. Holosun 507K

I’ve played with optics here and there but only recently dived in feet first into serious carry optics.

The P365 XL slide comes cut for a particular footprint, often called the Shield footprint, in honor of the fact the Shield was the first micro red dot.

The Holosun 507K fits this footprint and seems to be the most durable option on the market.

Sig Sauer P365 Upgrades Holosun 507K
Holosun 507K on the P365.

I turned to the internet and saw some failures with various other micro-optics. That said, the Holosun seemed to hold up the best.

I can now verify that the 507K is a well-made optic capable of withstanding a good deal of abuse. (Full review coming soon.)

Another reason I like the 507K is the built-in rear iron sight.

The P365 XL requires you to remove a rear plate that contains the rear Sight. The 507K’s built-in rear sight nub and the optic’s height allow it to naturally co-witness.

The multiple reticle options give you a big 32 MOA circle that’s absolutely huge and easy to get on target at self-defense ranges.

Holosun 507K rear
Holosun 507K

Look through the optic, put the dot on the target and go.

If you need more precision, the 2 MOA plain red dot is better at moderate and long ranges.

With the 507K, I’m faster and much more accurate. Red dots are wonderful additions to self-defense firearms and truly increase your capabilities. They blow iron sights out of the water.

Plus, you get a side-loading battery, and I love that. I hate removing an optic just to swap batteries.

at OpticsPlanet

Prices accurate at time of writing

Prices accurate at time of writing

5. Streamlight TLR 6 Light

Lights for tiny guns are rather rare at the moment, especially when your tiny gun has a proprietary rail system.

I don’t like the Olight, and the Surefire is tough to find. I have a TLR 7 SUB on the way, but the TLR 6 is my light of choice until then.

TLR-6 with Push-Button

I’ve had one for well over a year now, and it’s yet to let me down.

It’s been abused, used, and present for daily carry for quite some time. The slim build means hardly any bulk added to the gun.

Sig Sauer P365 Upgrades Light On
We like lights!

On top of that, the TLR 6 has been popular enough to warrant the holster manufacturer’s attention. You can find a holster that fits with the light rather easily.

Dual buttons form ambidextrous controls that sit in a position that makes them easy to reach with a trigger finger or your off-hand thumb.

The TLR 6 is a combination of laser and light, and you can use the buttons to alternate between three different modes. Modes include light and laser, light only, and laser only.

My only issue is that the light is only 100 lumens. That’s not a ton of power for the light to have, and it only works at extremely close ranges.

Sig Sauer P365 Upgrades Light

I treat it as more of a backup light called upon when my handheld light is down or inaccessible.

The laser is a handy aiming option should I be unable to use my optic or sights. It’s also fun to fire accurately from the hip, ringing steel and punching paper.

The brighter, more powerful TLR 7 SUB may replace the TLR 6, but that won’t be until I properly test it…and I can find a holster.

at Amazon

Prices accurate at time of writing

Prices accurate at time of writing

What do you think about the TLR 6? Rate it below!

6. MagGuts +2

Sig’s success was built on the magazine design and its ability to hold a multitude of rounds.

The P365 originally held 10 rounds, but Sig released a 12-, then a 15-round magazine in short order.

Sig Sauer P365 Upgrades Mags
All the mags.

The 12-round magazine is my personal favorite and offers substantial ammunition with a slight extension that gives me a better grip on the gun.

The 10- rounder with the flush baseplate is the most concealable magazine, and I think it serves a purpose if you ankle or pocket carry.

That doesn’t mean the 15-rounder doesn’t have a place in the grand scheme of things. To me, it’s the perfect option to carry a reload with.

Sig Sauer P365 Upgrades Mags
All the rounds…

It fits in my pocket, and there are tons of magazine holders out there that fit it. This includes Neomag, which makes the best pocket reload option.

Why not carry a reload with a few extra rounds?

It’s not hard to conceal and gives you a ton more ammo should you need to reload.

MagGuts recently released +2 MagGuts for the P365’s 10-, 12-, and 15-round magazines.

To be clear, these are not magazine extensions. Nope, they are literally magazine guts that replace your internal spring, follower, and magazine base plate.

Sig Sauer P365 Upgrades Mag Guts
MagGuts +2

They add no extra length to your magazines but allow you to add two extra rounds to each magazine. My short 10-round magazine now holds 12-rounds. My favorite 12-round magazine now houses 14-rounds.

This allows my subcompact P365 to now have near the same capacity as a Glock 19.

Installation took no time at all, and my magazines were actually easier to load.

After installation, I dumped rounds out of these things to ensure reliability before I carried it.

After 300 rounds without issue, I felt confident enough to carry them.

Those two extra rounds are a big deal to me. Honestly, I think every P365 magazine should have MagGuts in them.

at MagGuts

Prices accurate at time of writing

Prices accurate at time of writing

7. Promag Drum

Promag has recently released a magazine to conquer all!

The P365 now has a drum, a 50-round drum, to be specific. It’s as ridiculous as you think it is.

Is it useful? No, not really.

Sig Sauer P365 Upgrades
This just looks cool.

Will it replace my spare mag I keep for emergency reloads? No.

Is it practical in any way? Nah, of course not.

It’s just fun and silly, making the gun look ridiculous!

Sig Sauer P365 Upgrades Drum Mag
Tell me this isn’t rad…you can’t!

But, upside, it’s also reliable. I put two full drums through this bad boy, and it worked without a hitch.

A hundred rounds aren’t much, admittedly, but stressing testing a range toy is silly.

It’s frustration-free so far, but I wouldn’t put it through a mud, sand, and ice test.

at GunMag Warehouse

Prices accurate at time of writing

Prices accurate at time of writing


My ultimate P365 offers better control with the comp and long slide, easier aiming with the red dot and laser, substantial capacity with my magazine options — moving from a traditional concealed carry gun to something a little more effective for fighting.

It went from subcompact carry gun to fighting pistol in just a few upgrades.

Sig Sauer P365 Upgrades

My ultimate Sig Sauer P365 admittedly shed some of its compact stylings. It’s grown in size but can reconvert to something more akin to a pocket pistol if needed.

What about concealment? Not an issue with a good holster.

Do you agree with my upgrades or disagree with the P365 extras? Let me know below what you think, and let me know what you would change! If you want more on the P365 and to see why there’s so much fuss, check out our full review here. Or to read more on its big brother, see our Sig Sauer P320 review.

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17 Leave a Reply

  • Scott

    I have not yet gotten my P365 XL, but I do plan to make it my EDC. As someone with big hands, the 15 round mag is mandatory for me to use it. I love the idea of the threaded barrel and comp. I had pondered using the Romeo Zero, but if the Holosun 507k is more durable and they are competitive in price, that might be in the plan too. I do not need the light even if I like the look of it. I would say the same for any EDC unless it is open-carried. (I can shine a separate light at someone without appearing to draw down on them.) But here is my question: What holster would accommodate this set-up without compromising the concealment? I have been considering the Uban Cary G3. Can anyone advise on how that works, or doesn't?

    14 minutes ago
  • Daniel Thomas

    DBThomas I originally purchased the 1st iteration of the P365. I was impressed how it felt in the hand, operationally sweet! Then I hit the range. I'm 69, still active as a finish carpenter and Kitchen installer. Age and physical abuse has taken a toll on my grip. Tried a double tap out of the box. The muzzle rise on the 2nd shot went high, at least high enough to scare me. Ok then! This was a platform that needed a much stronger grip to keep under control. (For me). So grip it I did!!! I could shoot consistent kill zone groupings at 5-15 yards all day long. What came up for me was that an EDC is an emergency use weapon. I got to thinking that I didnt want to rapid draw 'AND' also think about my grip. Then the XL came out. Longer butt, longer barrel for better accuracy. Sold the original and ordered the XL. I was using the iron sites on both. The XL was shooting 4-6" higher using the sights. Took a little getting used to. So now I have to concentrate on shooting lower instead of grip and muzzle rise!!! LOL!!! In any case I regret selling the original. Both these 365 SIGs are great carry guns. I do want to go with the Holosun optic. I've read elsewhere that these are a great addition to the 365. Just so you know, my impression of your build is a great shooting handgun but for a 'Compact Carry' its a bit like a 'Full Dress Harley'!!!

    15 hours ago
  • KT

    Anyone tried one of the Icarus Precision grip modules? I'm pretty curious about them. Made from aluminum, with a beaver tail and 1913 picatinny rail so you have more light options. Idk, might be awesome

    16 hours ago
    • Matt

      Best upgrade for the P365 after the flat trigger. Kinda spendy but it turns the poly into a full metal gun adding a little extra recoil reducing weight. Oh! And picatinny rail, extended beaver tail and three colors. Badabing! It's a beautiful thing

      1 minute ago
  • MRKing

    Travis, I took a different route upgrading my p365, but I’m (mostly) happy with my mods, too. I sent my slide to Jaegerwerks and had it dovetail milled for the Holosun 507k. That let me keep the factory sights, although I am now leaning toward swapping for suppressor-height sights because it’s bottom 1/3 co-witness and I’d really prefer them to be taller. I also upgraded to the flat trigger so that it would feel the same as my p365XL, and because I shot tighter groups with the flat trigger. (Swapped first from my XL before I bought another one... I don’t understand why Sig went flat in the XL and curved in the little guy???). I’ve not added a light or laser - the gun is already heavy enough with the larger mag and I just don’t want any more weight on my EDC. (And no, I don’t want to hear people criticize me for liking a light weight EDC gun. Keep your snarkiness in check, folks.) I’m also thinking about grabbing a SAS slide. Not sure I’d ever want to pocket carry the 365 - I have a .380 that pocket carries well. But it might be nice to try. Regardless, thanks for sharing your mods. I may look into that barrel and comp!

    17 hours ago
  • Josh

    I'm sorry, I'm sorry...unrealistically, over-the-top customization for a SUBCOMPACT gun. This is immensely impractical at every level, you're going to spend an absolute fortune doing this, and at the end of the day, you've compromised the entire philosophy of the gun. This is just a dumb idea. Don't do any of this to your 365. Grab yourself a 320 if you have to customize the crap out of it, but Sig made the 365 for a specific reason, and it was absolutely zero of these.

    18 hours ago
    • Eric

      I concur, have a p365, no modifications necessary for ccw, it’s perfect the way it is and any changes defeat it’s des for ccs, if you have a pistol you keep for home defense or competition shoot by all means do upgrades you like

      16 hours ago
    • Shawn

      I completely disagree... All due respect but I love the fit and feel of the p365xl in my hand and am waiting for my Griffin Arms threaded barrel with Micro Carry Comp. (Optics Planet $176 with tax and shipping for the pair)

      This will do nothing to hinder the concealability of this gun and only improve accuracy and recoil.

      I have the p320 x-compact with Romeo 1-Pro and O-Light Baldr Mini and my goal for it was for carry purposes. I do carry it if printing is not a concern but the p365xl sits super comfortable with little to no obvious printing.

      The nominal amount of barrel length I am adding to this gun will only make it better for what it is: An EDC tool for self defense purposes that is accurate, comfortable to shoot, easy to carry and fun to train with...

      You have your opinion, I have mine... God Bless America!!!

      16 hours ago
    • Conserve Liberty

      That’s what I thought. Plain 365 with MTS + 10rd extended mag. Pocket, ankle or AIWB carry. I do carry a 10rd spare mag LH IWB so I think changing to a 12rd is a good idea.

      16 hours ago
    • Matt

      Disagree, the light and rds are great additions that don't affect concealment. Have them on my daily carry 365xl. The mag guts is a cool idea, I use the 12 round mag with no issue but I'd consider purchasing One for my 10 round mag.

      8 hours ago
    • Travis Pike

      If you read the article before racing to the comments you'd see the original subcompact form of the P365 is still an option since I have the slide and frame to do so.

      Why did SIG make the XL if it's supposed to be such a small gun?

      6 hours ago
  • SigEspo

    Ever have issues with the mag guts follower? Received 2... 1 sits flush where it should, the other sits significantly higher causing issues with jams.

    18 hours ago
  • Ram

    It's unclear from the article - does the P320 FCU fit the P365 frame? Does Sig even sell the P365 FCU separately or do you mean you are using your existing Sig P365 FCU and swapping that out to various frames?

    20 hours ago
    • John

      He used the P320 FCU on the P365 frame, and according to the article, it’s swappable with other frames.

      18 hours ago
      • Dave

        No he didn’t use the 320 fcu in the 365. They’re completely different sizes with the 320 fcu being a good inch longer as well as wider. He just swapped his 365 fcu between frames.

        17 hours ago
    • Dave

      The 320 FCU is too large (1” +/- too long and too wide/thick) to use in a 365. He just swapped his 365 fcu between frames.

      17 hours ago
    • Michael

      They are two separate FCU they are not interchangeable to my knowledge,

      16 hours ago
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