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?
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.
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
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 
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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!
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.
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.
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.