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12/7/2025 10:29:56 AM EDT
[Last Edit: ELittlefield][Edited]
A Smaller Flux Raider: The 365UL


https://fluxdefense.com/shop/raider-365-ultralight?attribute_color=BLACK&attribute_holster=Black+%28Included+%2B+%240.00%29

Hi guys, I'm very interested in the 365 PDW concept. I currently own a P365 X Macro, with the barrel a bit shorter than the slide, and cutouts in the slide to act as a compensator, and a mag well for 17 round X Macro magazines.

Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.

" />

Thanks guys!
12/7/2025 10:35:48 AM EDT
[Last Edit: dmk0210][Edited] [#1]
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
View Quote
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations. Yours appears to have no external thumb safety, so you should be GTG to fit anything made for the P365.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.

EDIT:  Actually, according to the website your slide won't work:

https://fluxdefense.com/shop/raider-365-ultralight
Important Compatibility Notes:

Do not use short (standard) P365 slides.
Recommended slides: P365XL, TACOPS or P365 FUSE.
Works with 17, 21, 25 round P365 magazines.
Not compatible with 12–15 round magazines.
Suppressor Clearance – Designed with ample space to accommodate most common pistol suppressors without interference
Original aluminum R365 holster and magwells are not compatible with the Ultralight.
View Quote


12/7/2025 10:37:59 AM EDT
[#2]
Quote History
Originally Posted By dmk0210:
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.

View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By dmk0210:
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.


Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?
12/7/2025 10:46:08 AM EDT
[#3]
Quote History
Originally Posted By ELittlefield:

Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By ELittlefield:
Originally Posted By dmk0210:
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.


Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?


17, yes.
True Precision is what you want for the barrel.
https://true-precision.com/pre-order-extended-sig-sauer-p365-threaded-barrel-for-6-5-chassis-systems/
If you are going to run a suppressor you need to get the recoil spring tuning kit (these barrels are significantly longer than the slides). Some people have reported destroying the barrel running it supressed hard.
"My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori." -Wilfred Owen
12/7/2025 10:48:43 AM EDT
[#4]
Quote History
Originally Posted By Bye_Felicia:


17, yes.
True Precision is what you want for the barrel.
https://true-precision.com/pre-order-extended-sig-sauer-p365-threaded-barrel-for-6-5-chassis-systems/
If you are going to run a suppressor you need to get the recoil spring tuning kit (these barrels are significantly longer than the slides). Some people have reported destroying the barrel running it supressed hard.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
Originally Posted By dmk0210:
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.


Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?


17, yes.
True Precision is what you want for the barrel.
https://true-precision.com/pre-order-extended-sig-sauer-p365-threaded-barrel-for-6-5-chassis-systems/
If you are going to run a suppressor you need to get the recoil spring tuning kit (these barrels are significantly longer than the slides). Some people have reported destroying the barrel running it supressed hard.

I see. This may not be quite as easy as I was imagining. Thanks!
12/7/2025 10:49:38 AM EDT
[#5]
XL 365 Barrel vs the True Precision Barrel she told you not to worry about.
Attached File


True Precision installed in an Aluminum Raider;
Attached File
"My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori." -Wilfred Owen
12/7/2025 10:55:48 AM EDT
[#6]
Quote History
Originally Posted By ELittlefield:

I see. This may not be quite as easy as I was imagining. Thanks!
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By ELittlefield:
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
Originally Posted By dmk0210:
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.


Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?


17, yes.
True Precision is what you want for the barrel.
https://true-precision.com/pre-order-extended-sig-sauer-p365-threaded-barrel-for-6-5-chassis-systems/
If you are going to run a suppressor you need to get the recoil spring tuning kit (these barrels are significantly longer than the slides). Some people have reported destroying the barrel running it supressed hard.

I see. This may not be quite as easy as I was imagining. Thanks!


I haven't tried running mine suppressed yet, but I'm likely going with just a micro comp. I have the larger 320 flux setup with a suppressor and its not bad; but with the suppressor it doesn't seem as worth it when compared to something like my MP5-RS that I can use a trilug on.
"My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori." -Wilfred Owen
12/7/2025 10:57:46 AM EDT
[#7]
Originally Posted By ELittlefield:
https://www.youtube.com/watch?v=RPmjbEdcUZY

https://fluxdefense.com/shop/raider-365-ultralight?attribute_color=BLACK&attribute_holster=Black+%28Included+%2B+%240.00%29

Hi guys, I'm very interested in the 365 PDW concept. I currently own a P365 X Macro, with the barrel a bit shorter than the slide, and cutouts in the slide to act as a compensator, and a mag well for 17 round X Macro magazines.

Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.

https://i.imgur.com/CI6zkHQ.jpeg" target="_blank">https://i.imgur.com/CI6zkHQ.jpeg

Thanks guys!
View Quote


Just noticed you have the comp version. If it's like the 320 comp you need to verify it'll work with a longer barrel. My Legion 320 Flux I swapped the slide out because the integrated comp prevented you from using a longer barrel.
"My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori." -Wilfred Owen
12/7/2025 10:59:30 AM EDT
[#8]
Quote History
Originally Posted By Bye_Felicia:


I haven't tried running mine suppressed yet, but I'm likely going with just a micro comp. I have the larger 320 flux setup with a suppressor and its not bad; but with the suppressor it doesn't seem as worth it when compared to something like my MP5-RS that I can use a trilug on.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
Originally Posted By dmk0210:
Originally Posted By ELittlefield:
Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.
There is no difference in the FCUs except for those with an external thumb safety and those with no thumb safety. That's the whole point of the modular FCU. One "gun / FCU", many different configurations.

I'm not sure about the slide. It should work, but may be a bit short and look weird. You should probably get a long FUSE slide and barrel for a PDW. There are also some aftermarket long 6" barrels made for PDW use.


Understood, thank you. My plan is to get a threaded barrel and suppress it with my Rugged Obsidian 45, in short configuration.

Will my 17 round magazines work in this?


17, yes.
True Precision is what you want for the barrel.
https://true-precision.com/pre-order-extended-sig-sauer-p365-threaded-barrel-for-6-5-chassis-systems/
If you are going to run a suppressor you need to get the recoil spring tuning kit (these barrels are significantly longer than the slides). Some people have reported destroying the barrel running it supressed hard.

I see. This may not be quite as easy as I was imagining. Thanks!


I haven't tried running mine suppressed yet, but I'm likely going with just a micro comp. I have the larger 320 flux setup with a suppressor and its not bad; but with the suppressor it doesn't seem as worth it when compared to something like my MP5-RS that I can use a trilug on.

Your replies are very helpful, thank you. I think I'll reorient my idea of putting a suppressor on it. I have this thing with an FRT if I want a little more firepower. 3 lug is an awesome mounting system.

" />

I'll rethink getting one to see if it makes sense as an unsuppressed gun.
12/7/2025 10:59:52 AM EDT
[#9]
Quote History
Originally Posted By Bye_Felicia:


Just noticed you have the comp version. If it's like the 320 comp you need to verify it'll work with a longer barrel. My Legion 320 Flux I swapped the slide out because the integrated comp prevented you from using a longer barrel.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
https://www.youtube.com/watch?v=RPmjbEdcUZY

https://fluxdefense.com/shop/raider-365-ultralight?attribute_color=BLACK&attribute_holster=Black+%28Included+%2B+%240.00%29

Hi guys, I'm very interested in the 365 PDW concept. I currently own a P365 X Macro, with the barrel a bit shorter than the slide, and cutouts in the slide to act as a compensator, and a mag well for 17 round X Macro magazines.

Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.

https://i.imgur.com/CI6zkHQ.jpeg" target="_blank">https://i.imgur.com/CI6zkHQ.jpeg

Thanks guys!


Just noticed you have the comp version. If it's like the 320 comp you need to verify it'll work with a longer barrel. My Legion 320 Flux I swapped the slide out because the integrated comp prevented you from using a longer barrel.

Roger that.
12/7/2025 11:01:27 AM EDT
[Last Edit: dmk0210][Edited] [#10]
I just watched the video again after a second cup of caffeine.

Now I think I want one of these with an ACOG on it.
12/7/2025 11:02:00 AM EDT
[#11]
Quote History
Originally Posted By ELittlefield:

Roger that.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By ELittlefield:
Originally Posted By Bye_Felicia:
Originally Posted By ELittlefield:
https://www.youtube.com/watch?v=RPmjbEdcUZY

https://fluxdefense.com/shop/raider-365-ultralight?attribute_color=BLACK&attribute_holster=Black+%28Included+%2B+%240.00%29

Hi guys, I'm very interested in the 365 PDW concept. I currently own a P365 X Macro, with the barrel a bit shorter than the slide, and cutouts in the slide to act as a compensator, and a mag well for 17 round X Macro magazines.

Will my slide, barrel, and serial numbered FCU drop into this braced chassis? I'm a little unclear whether this is only made to work with the slimmer original P365, and I'm unsure what my slide is called in Sig's nomenclature.

https://i.imgur.com/CI6zkHQ.jpeg" target="_blank">https://i.imgur.com/CI6zkHQ.jpeg

Thanks guys!


Just noticed you have the comp version. If it's like the 320 comp you need to verify it'll work with a longer barrel. My Legion 320 Flux I swapped the slide out because the integrated comp prevented you from using a longer barrel.

Roger that.



Looks like you could use this barrel, with no shroud if you want to go supressed (assuming you have a small enough diameter can).
"My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori." -Wilfred Owen
12/7/2025 11:05:22 AM EDT
[Last Edit: dmk0210][Edited] [#12]
Quote History
Originally Posted By Bye_Felicia:


I haven't tried running mine suppressed yet, but I'm likely going with just a micro comp. I have the larger 320 flux setup with a suppressor and its not bad; but with the suppressor it doesn't seem as worth it when compared to something like my MP5-RS that I can use a trilug on.
View Quote
Yeah, looking critically at the 320 version, it doesn't seem like it would have any advantage over a really small MP5k or AR PDW build (except for mag commonality). I've put that one in the cart and taken it out again over and over for a year now.

This little thing would make a hell of a BUG to a P365 pocket gun either off body, in a the glovebox, stashed somewhere, etc.

Or in a shoulder holster like the Secret Service Uzi during the assignation attempt on Reagan.

12/7/2025 4:04:18 PM EDT
[#13]
Quote History
Originally Posted By ELittlefield:

Will my 17 round magazines work in this?
View Quote


FYI: If you are looking to buy mags or already have Magpul mags, I just found this:

https://www.reddit.com/r/FluxDefense/comments/1pgajkd/magpul_amag_17rd_are_incompatible_with_both_flux/
12/10/2025 12:17:34 PM EDT
[#14]
Quote History
Originally Posted By dmk0210:
Yeah, looking critically at the 320 version, it doesn't seem like it would have any advantage over a really small MP5k or AR PDW build (except for mag commonality). I've put that one in the cart and taken it out again over and over for a year now.

This little thing would make a hell of a BUG to a P365 pocket gun either off body, in a the glovebox, stashed somewhere, etc.

Or in a shoulder holster like the Secret Service Uzi during the assignation attempt on Reagan.
View Quote

FWIW the USSS Uzi pictured at the Reagan assassination attempt was in a case, not a shoulder holster.  You can see the case with an Uzi foam cutout on the ground in the righthand side of the photo here.
12/10/2025 8:34:04 PM EDT
[#15]
There is also a Sig OEM polymer version with the FCU, 6" barrel, and mags that was supposed to be out month(s) ago.  I've been waiting for this one as not going to convert the 365s I have now and hoping the math is slightly better than 'building' one from scratch.  There were going to be three models including one with a red dot; now it looks like just two models; one standard, and a tac-pac with extra mags including a 25-rounder.

FWIW, I've saved some money with Sig Connect -- hate buying ($80) into something like that, but between a grip module and all the mags I have bought for me and family it made sense. Saves $10 on the 17-round magazines and $14 on the 25-rounders -- more on some of the grip modules



1/27/2026 9:25:46 PM EDT
[#16]
I'm starting to come back around to this. To anyone who has used the aluminum and polymer frames, which do you prefer?
1/31/2026 10:33:57 PM EDT
[#17]
Got a chance to play with one of these................I think I want one
"The villainy you teach me, I will execute, and it shall go hard but I will better the instruction"
5/2/2026 7:50:28 AM EDT
[#18]
I ordered an aluminum frame. I'm in it now.
5/2/2026 5:40:11 PM EDT
[#19]
Quote History
Originally Posted By ELittlefield:
I ordered an aluminum frame. I'm in it now.
View Quote


Did you order a aluminum FLUX frame or Sig P365 aluminum frame? With the responses it is hard to tell. I am interested in getting a FLUX frame for my P365 as well and wasn't sure what you have in mind.

I do have a P320 FLUX Raider and I love it. It is a very nice design and more compact compared to other pcc, all things considered. I wish they could make one for the P365 like the P320.
Be the change you want in this world.
5/2/2026 5:45:48 PM EDT
[#20]
Quote History
Originally Posted By patw:


Did you order a aluminum FLUX frame or Sig P365 aluminum frame? With the responses it is hard to tell. I am interested in getting a FLUX frame for my P365 as well and wasn't sure what you have in mind.

I do have a P320 FLUX Raider and I love it. It is a very nice design and more compact compared to other pcc, all things considered. I wish they could make one for the P365 like the P320.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By patw:
Originally Posted By ELittlefield:
I ordered an aluminum frame. I'm in it now.


Did you order a aluminum FLUX frame or Sig P365 aluminum frame? With the responses it is hard to tell. I am interested in getting a FLUX frame for my P365 as well and wasn't sure what you have in mind.

I do have a P320 FLUX Raider and I love it. It is a very nice design and more compact compared to other pcc, all things considered. I wish they could make one for the P365 like the P320.

A P365 aluminum frame.
5/7/2026 10:25:49 PM EDT
[#21]
Ohhhhhhhhh yeah. This thing is sex on a stick.

I think I'll roll with my factory, compensated X Macro slide, once I get my 3.7" barrel. Based on reports, I don't think I will bother trying to suppress it. This thing's real advantage is ultimate concealability from a braced gun. I'll lean into that.

" />
" />
" />
5/8/2026 7:31:15 PM EDT
[#22]
I've also ordered a True Precision 6" barrel.
5/9/2026 7:21:46 PM EDT
[#23]
As feared, the X Macro slide with comp cuts does not permit a full length barrel.

Fuck me, this is getting expensive. Oh well, once I buy another FCU, at least I'll have an entire pistol's worth of parts that didn't work with the FLUX.
5/12/2026 8:59:42 AM EDT
[Last Edit: ROCK6][Edited] [#24]
Quote History
Originally Posted By ELittlefield:
As feared, the X Macro slide with comp cuts does not permit a full length barrel.

Fuck me, this is getting expensive. Oh well, once I buy another FCU, at least I'll have an entire pistol's worth of parts that didn't work with the FLUX.
View Quote

@ELittlefield
Don't worry bro, I'm right there with you. Just got my Raider UL yesterday and slapped my P365XL upper on it to test it out as I wait for a "new" P365XL to get get delivered. I found a FUSE threaded barrel, which may not work on the P365XL slide, so I found a spare FUSE slide on Ebay. Of course, my threaded barrel is only 5.3" and doesn't clear the shroud, so I said fucked it and ordered the True Precision 6.5" threaded barrel. At least I have a spare optic sitting unused

Flux P365 Raider UL
Used P365XL (jsut for the FCU, it was only $50 more than a new FCU...of course now I'm tempted to just get a new FCU)
FUSE threaded  barrel (5.3")
FUSE upper slide assembly
Tru-Precision 6.5" barrel

Oh, and while I have plenty of 17rd mags for P365/X/XL, I didn't have have any set up for the Raider, so I ordered some Magpul 17-rounders a few 21 OEM mags and one 25 round OEM mag.

Nice little PDW turned into a damn many trap and I'll probably end up with a couple of new handguns

I'll shoot a few rounds this afternoon (take a couple of pics) after work. I had to take the shroud off to run the Spectre 9k, so we'll see if that cycles okay on the Flux.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/14/2026 7:20:49 AM EDT
[#25]
Quote History
Originally Posted By ROCK6:

@ELittlefield
Don't worry bro, I'm right there with you. Just got my Raider UL yesterday and slapped my P365XL upper on it to test it out as I wait for a "new" P365XL to get get delivered. I found a FUSE threaded barrel, which may not work on the P365XL slide, so I found a spare FUSE slide on Ebay. Of course, my threaded barrel is only 5.3" and doesn't clear the shroud, so I said fucked it and ordered the True Precision 6.5" threaded barrel. At least I have a spare optic sitting unused

Flux P365 Raider UL
Used P365XL (jsut for the FCU, it was only $50 more than a new FCU...of course now I'm tempted to just get a new FCU)
FUSE threaded  barrel (5.3")
FUSE upper slide assembly
Tru-Precision 6.5" barrel

Oh, and while I have plenty of 17rd mags for P365/X/XL, I didn't have have any set up for the Raider, so I ordered some Magpul 17-rounders a few 21 OEM mags and one 25 round OEM mag.

Nice little PDW turned into a damn many trap and I'll probably end up with a couple of new handguns

I'll shoot a few rounds this afternoon (take a couple of pics) after work. I had to take the shroud off to run the Spectre 9k, so we'll see if that cycles okay on the Flux.

ROCK6
View Quote View All Quotes
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Quote History
Originally Posted By ROCK6:
Originally Posted By ELittlefield:
As feared, the X Macro slide with comp cuts does not permit a full length barrel.

Fuck me, this is getting expensive. Oh well, once I buy another FCU, at least I'll have an entire pistol's worth of parts that didn't work with the FLUX.

@ELittlefield
Don't worry bro, I'm right there with you. Just got my Raider UL yesterday and slapped my P365XL upper on it to test it out as I wait for a "new" P365XL to get get delivered. I found a FUSE threaded barrel, which may not work on the P365XL slide, so I found a spare FUSE slide on Ebay. Of course, my threaded barrel is only 5.3" and doesn't clear the shroud, so I said fucked it and ordered the True Precision 6.5" threaded barrel. At least I have a spare optic sitting unused

Flux P365 Raider UL
Used P365XL (jsut for the FCU, it was only $50 more than a new FCU...of course now I'm tempted to just get a new FCU)
FUSE threaded  barrel (5.3")
FUSE upper slide assembly
Tru-Precision 6.5" barrel

Oh, and while I have plenty of 17rd mags for P365/X/XL, I didn't have have any set up for the Raider, so I ordered some Magpul 17-rounders a few 21 OEM mags and one 25 round OEM mag.

Nice little PDW turned into a damn many trap and I'll probably end up with a couple of new handguns

I'll shoot a few rounds this afternoon (take a couple of pics) after work. I had to take the shroud off to run the Spectre 9k, so we'll see if that cycles okay on the Flux.

ROCK6

The Youtuber Brass Facts said in a video that you'll spend 2 grand on this thing. I scoffed, and said "bro it's only 650 bucks I already have the parts."

Yeah. Real big brain on ELittlefield.
5/14/2026 8:39:15 AM EDT
[#26]
Quote History
Originally Posted By ELittlefield: As feared, the X Macro slide with comp cuts does not permit a full length barrel.

Fuck me, this is getting expensive. Oh well, once I buy another FCU, at least I'll have an entire pistol's worth of parts that didn't work with the FLUX.
View Quote


Can you Dremel the inside & make it work?
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
5/14/2026 9:33:02 AM EDT
[#27]
Quote History
Originally Posted By backbencher:


Can you Dremel the inside & make it work?
View Quote View All Quotes
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Quote History
Originally Posted By backbencher:
Originally Posted By ELittlefield: As feared, the X Macro slide with comp cuts does not permit a full length barrel.

Fuck me, this is getting expensive. Oh well, once I buy another FCU, at least I'll have an entire pistol's worth of parts that didn't work with the FLUX.


Can you Dremel the inside & make it work?

Possibly. I’m not taking a dremel to to the muzzle of the side though, which might in the future support a barrel bearing a silencer. Indeed I just had a Hux Flow 9 approved, which may fit this gun well. Incredibly lightweight, and low back pressure.
5/14/2026 10:37:09 PM EDT
[Last Edit: ELittlefield][Edited] [#28]
My Fuse slide arrived, and the optic cut has different size threaded holes from my factory X Macro slide.

Oh goodie. Another 13 dollars, and another 4-6 day wait.

I am losing hope that I will ever fire this gun. Why in the hell are there different screw thread patterns in a standardized optic footprint??? And if there are, why would the Fuse slide not come with them?


I dug through some old optic boxes, and found a set of screws that seems to work. Test firing will commence tomorrow.
5/16/2026 12:31:04 AM EDT
[#29]
Snappy. Extremely snappy. I would not care to shoot this for a long range session. The shoulder recoil is astonishing for a 9mm, and the brace smacks me in the face. I'm sure I'll try to adjust my stance in the future. In 32 rounds, I had one failure to fully chamber, no big deal. If it's still happening after a hundred or two hundred rounds I'll address it.
5/16/2026 12:50:24 AM EDT
[#30]
Quote History
Originally Posted By ELittlefield:  Snappy. Extremely snappy. I would not care to shoot this for a long range session. The shoulder recoil is astonishing for a 9mm, and the brace smacks me in the face. I'm sure I'll try to adjust my stance in the future. In 32 rounds, I had one failure to fully chamber, no big deal. If it's still happening after a hundred or two hundred rounds I'll address it.
View Quote


Lightweight 9mm carbines seemingly have much more recoil than expected.
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
5/16/2026 7:06:19 AM EDT
[#31]
Quote History
Originally Posted By ELittlefield:
Snappy. Extremely snappy. I would not care to shoot this for a long range session. The shoulder recoil is astonishing for a 9mm, and the brace smacks me in the face. I'm sure I'll try to adjust my stance in the future. In 32 rounds, I had one failure to fully chamber, no big deal. If it's still happening after a hundred or two hundred rounds I'll address it.
View Quote

There's a small learning curve. My UL did seem a bit snappy, but it wasn't bad. I've got the 6.5" threaded barrel in, and I should receive the FUSE slide today. I'll get it fixed up. Of course, now awaiting another FCU to get my XL back into operation

I've only tried my Spectre 9k which has cycled just fine with the XL slide/barrel. For now, I'm just running it on a Safariland holster set up and it works (of course, no suppressor). I haven't tried carrying AIWB yet, but it seems almost ridiculous, but I can see it working if you understand a few limitations.  

My hands aren't small, but Flux braces typically push the web of your hand lower, so reaching the safety on mine takes a little more attention. Depending on how you carry it, I like the safety. I don't like to keep my Glock Flux or Glock Recover Tactical loaded with on in the chamber if I'm actually carrying them in a small bag. The P365 Flux kind of gives me a better sense of safety (yeah, feelings and shit). Overall, it's a very well-engineered package.  

I only have a short backstop for my backyard, where these PDWs shine is on a longer range with steel plates.




ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/17/2026 11:14:39 AM EDT
[#32]
Are the magazine extensions reasonably reliable?
5/17/2026 5:31:46 PM EDT
[#33]
Quote History
Originally Posted By ELittlefield:
Are the magazine extensions reasonably reliable?
View Quote

@ELittlefield, are you referring to the extended OEM mags? I've got some 21 rounders and a 25 rounder; all feed perfectly fine. I don't have enough time with the Magpul (stainless) 17 rounders, so time will tell.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/17/2026 5:34:13 PM EDT
[#34]
Quote History
Originally Posted By ROCK6:

@ELittlefield, are you referring to the extended OEM mags? I've got some 21 rounders and a 25 rounder; all feed perfectly fine. I don't have enough time with the Magpul (stainless) 17 rounders, so time will tell.

ROCK6
View Quote View All Quotes
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Quote History
Originally Posted By ROCK6:
Originally Posted By ELittlefield:
Are the magazine extensions reasonably reliable?

@ELittlefield, are you referring to the extended OEM mags? I've got some 21 rounders and a 25 rounder; all feed perfectly fine. I don't have enough time with the Magpul (stainless) 17 rounders, so time will tell.

ROCK6

I guess I was asking about extended base plates, but are there also long tube magazines from Sig themselves?
5/18/2026 7:36:03 AM EDT
[Last Edit: ROCK6][Edited] [#35]
Quote History
Originally Posted By ELittlefield:
I guess I was asking about extended base plates, but are there also long tube magazines from Sig themselves?
View Quote

@ELittlefield

I guess the Magpul mag base plates look bigger, but they're standard with their mags:

Magpul P365 mag

Sig has two OEM extended P365 mags, the 21 and 25 round mags:

Sig OEM 21-round mag

Sig OEM 25-round mag

All my P365s are the original P365, X or XL sizes. No Macro or full size grip frames, so all my P365 mags (a shit ton) don't fit the Flux. I had a few 21-rounders, but ended up grabbing some of the Magpul mags to see how they run (and they're cheaper than OEM and I don't want to dig around for the flush 17rd base-plates)

Magazine capacity is pretty versatile as I have some of older 15rd mags:

10rd, 12rd, 15rd, 17rd, 21rd and now 25rd

Oh, add some MagGuts and I have some 10+2 and 12+12 mags sprinked in

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/18/2026 7:59:30 AM EDT
[#36]
Quote History
Originally Posted By ROCK6:

@ELittlefield

I guess the Magpul mag base plates look bigger, but they're standard with their mags:

Magpul P365 mag

Sig has two OEM extended P365 mags, the 21 and 25 round mags:

Sig OEM 21-round mag

Sig OEM 25-round mag

All my P365s are the original P365, X or XL sizes. No Macro or full size grip frames, so all my P365 mags (a shit ton) don't fit the Flux. I had a few 21-rounders, but ended up grabbing some of the Magpul mags to see how they run (and they're cheaper than OEM and I don't want to dig around for the flush 17rd base-plates)

Magazine capacity is pretty versatile as I have some of older 15rd mags:

10rd, 12rd, 15rd, 17rd, 21rd and now 25rd

Oh, add some MagGuts and I have some 10+2 and 12+12 mags sprinked in

ROCK6
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By ROCK6:
Originally Posted By ELittlefield:
I guess I was asking about extended base plates, but are there also long tube magazines from Sig themselves?

@ELittlefield

I guess the Magpul mag base plates look bigger, but they're standard with their mags:

Magpul P365 mag

Sig has two OEM extended P365 mags, the 21 and 25 round mags:

Sig OEM 21-round mag

Sig OEM 25-round mag

All my P365s are the original P365, X or XL sizes. No Macro or full size grip frames, so all my P365 mags (a shit ton) don't fit the Flux. I had a few 21-rounders, but ended up grabbing some of the Magpul mags to see how they run (and they're cheaper than OEM and I don't want to dig around for the flush 17rd base-plates)

Magazine capacity is pretty versatile as I have some of older 15rd mags:

10rd, 12rd, 15rd, 17rd, 21rd and now 25rd

Oh, add some MagGuts and I have some 10+2 and 12+12 mags sprinked in

ROCK6

Nice, thank you.
5/18/2026 5:29:47 PM EDT
[#37]
Quote History
Originally Posted By ROCK6:
…but ended up grabbing some of the Magpul mags to see how they run….
View Quote


Interested in your experiences…I had heard the Magpuls did not work with the R365
5/19/2026 11:15:27 AM EDT
[#38]
Everything I've read was the shorter pistol baes plate adapters being finicky. Since all my OEM mags are used for the P365/X/XL, I haven't used any of the MagPul mags with their shorter baseplate adapters, just the standard 17rd mag (Macro/Fuse models), which has fed and fit fine in the Flux chassis grip.

To be fair, I’ve only used a few of the mags and only 10 rounds per mag. I did struggle to load a few up to the full 17 rounds as the spring is quite stiff. I need to get them all loaded and let them sit for a couple weeks.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/19/2026 12:23:23 PM EDT
[#39]


My SBR’d XMacro Flux Raider (aluminum):

Attached File


Attached File


I also have the True Precision threaded barrel:

Attached File


* don’t mind the charging handle where the optic cutout is…😎

The Sig 21 and 25 round mags are absolutely good to go.

It’s slightly better/easier to shoot with the SBR stock as opposed to the pistol brace but no question it’s snappy as some folks have mentioned…

I went with the forward mounted optic for reasons. Also, in this PCC-like configuration I feel a manual safety is mandatory and if you don’t have one you can add it very easily.

With the stock recoil spring I couldn’t get it to run with my OSS/HUXWRX Rad .45 can. I’m currently looking for something Ti/hyper light and booster less to run dedicated. Flux has an informative suppressor spreadsheet on their website where you can upload your personal experience as a guide/warning to others…

I’ve let a couple of people shoot it and activating the stock release and shooting steel at distance is fun and easy with it.
5/20/2026 12:41:24 PM EDT
[#40]
Quote History
Originally Posted By MikeWhiskey:
With the stock recoil spring I couldn’t get it to run with my OSS/HUXWRX Rad .45 can. I’m currently looking for something Ti/hyper light and booster less to run dedicated. Flux has an informative suppressor spreadsheet on their website where you can upload your personal experience as a guide/warning to others…

I’ve let a couple of people shoot it and activating the stock release and shooting steel at distance is fun and easy with it.
View Quote

Damn, that wrap makes it literally blend into the background of whatever tabletop it's sitting on!

I like that forward mount but I wanted to keep mine "holster friendly". I just got my FUSE slide yesterday and added the True Precision 6.5" threaded barrel so I could keep the shroud on the chassis.

No pictures yet, but like it. I'll have to rip a few rounds through it to test reliability today or tomorrow after work. I ran my XL slide (seen above) with a Spectre 9k and booster with zero issues and the OEM spring. I also have the direct threat SAW Shiv (very, very tiny and light), but want to keep my Griffin Armament Eze-Lok piston ecosystem consistent. I think the Spectre 9k will be dedicated if it proves to run reliably with the longer barrel.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
5/20/2026 1:21:13 PM EDT
[#41]
Quote History
Originally Posted By ROCK6:

Damn, that wrap makes it literally blend into the background of whatever tabletop it's sitting on!

I like that forward mount but I wanted to keep mine "holster friendly". I just got my FUSE slide yesterday and added the True Precision 6.5" threaded barrel so I could keep the shroud on the chassis.

No pictures yet, but like it. I'll have to rip a few rounds through it to test reliability today or tomorrow after work. I ran my XL slide (seen above) with a Spectre 9k and booster with zero issues and the OEM spring. I also have the direct threat SAW Shiv (very, very tiny and light), but want to keep my Griffin Armament Eze-Lok piston ecosystem consistent. I think the Spectre 9k will be dedicated if it proves to run reliably with the longer barrel.

ROCK6
View Quote

Flux was offering the grip wrap and “desert tiger stripe” is perfect for my environment.  The FDE chassis literally came out the day or two after I had ordered mine otherwise I would have gotten that one.  I also added the TiN extended slide and safety from Armory Craft…for reasons!

https://www.armorycraft.com/product-page/armory-craft-sig-sauer-p365-extended-slide-release

Attached File


Enhanced function AND pimp-tastic!

I also have Tactical Development’s slide racking plate which makes it extremely easy to rack the slide with the stock folded or press-check:

https://tactical.dev/products/f10-slide-racking-optic-plate-for-p365-slides?_pos=19&_sid=0ad73fe41&_ss=r

The forward mounted optic does prevent holster use but I decided I was going to SBR an aluminum chassis Flux Raider with the forward mounted optic and buy a polymer Flux Raider and keep the brace, mount an optic on the slide and run it in the holster they sell…

Likewise my plan with the can is to run it dedicated, thanks for posting your can experience and keep us posted with your test fire.
6/2/2026 4:17:14 AM EDT
[#42]
I got out and put another two magazines through it yesterday. It's an incredibly practical gun for the size, I am highly impressed. Just need to find some time to get the red dot zeroed.
6/2/2026 5:10:13 AM EDT
[#43]
I ordered a threaded barrel. I'm going to attempt using my Rugged Obsidian 45 in short configuration.
6/3/2026 10:47:37 AM EDT
[#44]
Quote History
Originally Posted By ELittlefield:
I ordered a threaded barrel. I'm going to attempt using my Rugged Obsidian 45 in short configuration.
View Quote

I just got to find some time, but I finally added True-Precision's 6.5" threaded barrel, put the Griffin Armament Eze-Lok muzzle adapter on it and it look like I'll be using the SiCo Spectre 9k the most with this little BDE. I need to do some shooting drills with it from the holster, but that will have to wait a couple weeks (I don't like to fire very much unsuppressed on my property).

The more I handle and shoot it, the more I'm like this setup.

The only damn problem with the FLUX:

I found a good deal on a P365XL and now have that FCU in my FLUX. BUT, now I have a new Wilson Combat frame (X/XL size), I have spare P365 barrels/recoil springs and found a used P365 slide with optics cut now on it's way which forced  me to buy new FCU and optic. I really need to just sell the XL slide assembly so I'm not tempted to grow that back into a handgun.

Currently:

2 x P365s
1 x P365Xs
2 x P365XLs
1 x FLUX/FUSE

1 x P365X getting assembled.

I'm all in on this platform, they work great for my patrolling kit (just LARPing property patrollling), great CCW that shoots well for me and now with a very viable, compatible PDW (I do have the FLUX with a Glock 17 and Recover Tactical with G34).



There may be a lot of bad shit about Sig Sauer, but the P365 ecosystem isn't one of them.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
6/3/2026 10:51:22 AM EDT
[#45]
Quote History
Originally Posted By ROCK6:

I just got to find some time, but I finally added True-Precision's 6.5" threaded barrel, put the Griffin Armament Eze-Lok muzzle adapter on it and it look like I'll be using the SiCo Spectre 9k the most with this little BDE. I need to do some shooting drills with it from the holster, but that will have to wait a couple weeks (I don't like to fire very much unsuppressed on my property).

The more I handle and shoot it, the more I'm like this setup.

The only damn problem with the FLUX:

I found a good deal on a P365XL and now have that FCU in my FLUX. BUT, now I have a new Wilson Combat frame (X/XL size), I have spare P365 barrels/recoil springs and found a used P365 slide with optics cut now on it's way which forced  me to buy new FCU and optic. I really need to just sell the XL slide assembly so I'm not tempted to grow that back into a handgun.

Currently:

2 x P365s
1 x P365Xs
2 x P365XLs
1 x FLUX/FUSE

1 x P365X getting assembled.

I'm all in on this platform, they work great for my patrolling kit (just LARPing property patrollling), great CCW that shoots well for me and now with a very viable, compatible PDW (I do have the FLUX with a Glock 17 and Recover Tactical with G34).

https://hosting.photobucket.com/3a5ba44e-72a5-4ded-b00a-39a4440c67c0/2d4b5fe0-34eb-43e8-88ab-1b3a57e31810.jpg?width=960&height=720&fit=bounds" target="_blank">https://hosting.photobucket.com/3a5ba44e-72a5-4ded-b00a-39a4440c67c0/2d4b5fe0-34eb-43e8-88ab-1b3a57e31810.jpg?width=960&height=720&fit=bounds

There may be a lot of bad shit about Sig Sauer, but the P365 ecosystem isn't one of them.

ROCK6
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By ROCK6:
Originally Posted By ELittlefield:
I ordered a threaded barrel. I'm going to attempt using my Rugged Obsidian 45 in short configuration.

I just got to find some time, but I finally added True-Precision's 6.5" threaded barrel, put the Griffin Armament Eze-Lok muzzle adapter on it and it look like I'll be using the SiCo Spectre 9k the most with this little BDE. I need to do some shooting drills with it from the holster, but that will have to wait a couple weeks (I don't like to fire very much unsuppressed on my property).

The more I handle and shoot it, the more I'm like this setup.

The only damn problem with the FLUX:

I found a good deal on a P365XL and now have that FCU in my FLUX. BUT, now I have a new Wilson Combat frame (X/XL size), I have spare P365 barrels/recoil springs and found a used P365 slide with optics cut now on it's way which forced  me to buy new FCU and optic. I really need to just sell the XL slide assembly so I'm not tempted to grow that back into a handgun.

Currently:

2 x P365s
1 x P365Xs
2 x P365XLs
1 x FLUX/FUSE

1 x P365X getting assembled.

I'm all in on this platform, they work great for my patrolling kit (just LARPing property patrollling), great CCW that shoots well for me and now with a very viable, compatible PDW (I do have the FLUX with a Glock 17 and Recover Tactical with G34).

https://hosting.photobucket.com/3a5ba44e-72a5-4ded-b00a-39a4440c67c0/2d4b5fe0-34eb-43e8-88ab-1b3a57e31810.jpg?width=960&height=720&fit=bounds" target="_blank">https://hosting.photobucket.com/3a5ba44e-72a5-4ded-b00a-39a4440c67c0/2d4b5fe0-34eb-43e8-88ab-1b3a57e31810.jpg?width=960&height=720&fit=bounds

There may be a lot of bad shit about Sig Sauer, but the P365 ecosystem isn't one of them.

ROCK6

I'm buying a threaded barrel designed for my 4.3" slide. I want to avoid the longer barrel, as in my mind with a can, it would increase the stress on the system. The weight being further out. I'd rather have a barrel that is supported by the slide right up to the threads. Perhaps I'm overthinking it, but that's my rationale.
6/5/2026 4:34:06 PM EDT
[#46]
Quote History
Originally Posted By ELittlefield:

I'm buying a threaded barrel designed for my 4.3" slide. I want to avoid the longer barrel, as in my mind with a can, it would increase the stress on the system. The weight being further out. I'd rather have a barrel that is supported by the slide right up to the threads. Perhaps I'm overthinking it, but that's my rationale.
View Quote

Yeah, I have a threaded FUSE barrel (shorter than the 6.5" threaded barrel). I'm going to tweak this a little as I wanted to keep the shroud on for now; anything shorter, I would have to dump the shroud.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson
6/10/2026 4:55:55 PM EDT
[#47]
A question for y'all, who does the engraving on the FCU for SBR registration? I've used Tar Heel State many times for AR receivers. How visible does the engraving need to be on a gun like this?
It was not preached to the crowd,
It was not taught by the State.
No man spoke it aloud,
When the English began to hate.
6/10/2026 5:19:31 PM EDT
[#48]
Quote History
Originally Posted By ELittlefield:
A question for y'all, who does the engraving on the FCU for SBR registration? I've used Tar Heel State many times for AR receivers. How visible does the engraving need to be on a gun like this?
View Quote

Just wait a few months and it won't be required.
6/10/2026 5:21:19 PM EDT
[#49]
Quote History
Originally Posted By CleverNickname:

Just wait a few months and it won't be required.
View Quote View All Quotes
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Quote History
Originally Posted By CleverNickname:
Originally Posted By ELittlefield:
A question for y'all, who does the engraving on the FCU for SBR registration? I've used Tar Heel State many times for AR receivers. How visible does the engraving need to be on a gun like this?

Just wait a few months and it won't be required.

Okay.
It was not preached to the crowd,
It was not taught by the State.
No man spoke it aloud,
When the English began to hate.
6/13/2026 8:19:59 AM EDT
[Last Edit: ROCK6][Edited] [#50]
So, I pulled off the Eze-Lok muzzle device and replaced the Spectre 9k with SAW shiv (no booster) and my 6.5" barrel Flux cycled flawlessly. Subsonic brass was only kicking out about 6-8" but it was doing it reliably. I think I just need to put some more rounds through the Flux/Fuse just to break it in. I did get the Armory Craft spring kit, but holding of doing any tuning until I can get another couple hundred rounds through it.

Ironically, I can get the Flux with Shiv into the holster and when I draw it out, it automatically (inadvertently?) deploys the brace. That's a nice feature.

I did have one issue with my Flux, the forward grip housing would drop the mag when shooting. Jake at Flux sent me a replacement kit, but I also found out that you can use an AR15 buffer tube stop spring, cutting it into two gives you a little more tension and length

For those unaware, the forward magazine holder is a double-release mechanism. You can use the thumb latch to release just that magazine, or you can use the grip mounted magazine slide button and if you push it forward far enough it will release the grip magazine and the forward mag at the same time. It's pretty effective at speed reloads and a nice feature whether you use it or not.

ROCK6
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants" - Thomas Jefferson

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