P365-380. FromP365-9

April 11, 2022, 10:33 AM

I have two 9mm p365s. If I buy a p365-380 barrel and recoil spring, am I able to convert my 9 to a 380? The two variants use the same FCU and grip module. Is the slide the same in both?

April 11, 2022, 11:53 AM

Stroonz

The 380 model has several things different.
First, the recoil spring is lighter: second the magazine has an added piece in the magazine to take up the space to accommodate the smaller 380 round. Additionally the 380 slide has lightening cuts into it to accommodate the lower power of the 380. Also the slide has a plate on top for an optic if you want to add one.

I would venture a guess that Sig will come out with an exchange kit containing a complete slide with barrel,spring, and magazines in the months to come

April 11, 2022, 12:55 PM

fquico

quote:
Originally posted by Stroonz:
[The 380 model has several things different.
First, the recoil spring is lighter: second the magazine has an added piece in the magazine to take up the space to accommodate the smaller 380 round. Additionally the 380 slide has lightening cuts into it to accommodate the lower power of the 380. Also the slide has a plate on top for an optic if you want to add one.]

I would venture a guess that Sig will come out with an exchange kit containing a complete slide with barrel,spring, and magazines in the months to come

Yet, it seems as though, but for the lightning cuts, that it should work with a 380 barrel and 380 recoil spring....

April 11, 2022, 01:20 PM

Stroonz

You will probably incur jams because because the slide may be too heavy to cycle with relatively underpowered 380 rounds.

How are going to get around the difference in magazines? Also I have not seen any source for the 380 barrel.

April 11, 2022, 01:37 PM

fquico

-stroonz, Sig has barrels and recoil springs in 380 for the 365. The mags to use are either the 380 mags and the 9 mags that supposedly do work.

April 11, 2022, 01:48 PM

12131

"supposedly".

According to Strader in SIG's intro video, the mags are slightly different.

But, the only way to know for sure is to try it out yourself.

April 11, 2022, 02:06 PM

Genorogers

quote:
Originally posted by 12131:
"supposedly".

According to Strader in SIG's intro video, the mags are slightly different.

But, the only way to know for sure is to try it out yourself.

The mags look the same except for a spacer in the rear of the internal of the mag because of the length of the 380. Ruger did the same to modify the LC9 mag to work in the LC380.

April 11, 2022, 02:10 PM

12131

quote:
Originally posted by Genorogers:
The mags look the same except for a spacer in the rear of the internal of the mag because of the length of the 380. Ruger did the same to modify the LC9 mag to work in the LC380.

Yeah, so they are not the same.

April 11, 2022, 02:21 PM

Genorogers

quote:
Originally posted by 12131:
quote:
Originally posted by Genorogers:
The mags look the same except for a spacer in the rear of the internal of the mag because of the length of the 380. Ruger did the same to modify the LC9 mag to work in the LC380.

Yeah, so they are not the same.

You are correct, just trying to explain the difference with what I see.

April 11, 2022, 02:39 PM

photohause

Why?

April 11, 2022, 03:27 PM

Stroonz

“Why?“. I will tell you why I’m switching to 380
I’m now 77 but still can do many things I used to. But, recently since my last range trip my arthritis really acts up, and I can barely rack the slide….not so with the 380. So as I age, I make adjustments.

April 11, 2022, 03:52 PM

Lefty Sig

Mag shells and floorplates are the same. Followers and lockplate/spacer are different, springs probably are too.

Slide is different, not just lightened but different profile on the top of the slide, oddball 8 front 6 rear irons, and shallower optic cut (due to lower profile) that doesn't allow cowitness with normal irons. Barrel is thinner wall so you can't drop in a .380 barrel into a 9mm slide.

A full top end will be like $400-450 so just get the whole gun for the relatively small difference.

April 11, 2022, 05:01 PM

Eaganite

quote:
Originally posted by Lefty Sig:

A full top end will be like $400-450 so just get the whole gun for the relatively small difference.

I would agree, you could sell your P365 9mm and buy the P365-380. Probably come out with little out of pocket.

April 11, 2022, 06:51 PM

Stroonz

^^^^^^^Thats exactly what I did.

April 11, 2022, 07:57 PM

hurst01

One problem I foresee is the cost of .380 is about half again what the 9mm is. I can buy a box of 9mm for about $20, I recently gave $38 for a box of .380. It is also harder to find lately.
I understand the Arthritis thing though, Good luck with what ever you do.

Ed

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April 12, 2022, 03:30 AM

TrojanX4

I've done the switch. You can take the P365 .380 slide and swap out the existing 9mm slide. The 9mm mags will work with .380 ammo but not super reliably. I had a few stove pipes initially but besides that I was able to shoot about 100 rounds after that without a hitch. I would recommend getting .380 mags, but in a pinch the 9mm mags work well enough for the range.

April 12, 2022, 03:55 AM

12131

quote:
Originally posted by TrojanX4:
I've done the switch. You can take the P365 .380 slide and swap out the existing 9mm slide. The 9mm mags will work with .380 ammo but not super reliably. I had a few stove pipes initially but besides that I was able to shoot about 100 rounds after that without a hitch. I would recommend getting .380 mags, but in a pinch the 9mm mags work well enough for the range.

Question OP had is if you can use the .380 barrel & RSA in the 9mm slide. Since you have both, do you know if that works?

April 12, 2022, 09:02 AM

TrojanX4

quote:
Originally posted by TrojanX4:
quote:
Originally posted by 12131:Question OP had is if you can use the .380 barrel & RSA in the 9mm slide. Since you have both, do you know if that works?

Thanks for clarifying Q, I guess I read the OP's post too quickly. And the answer is no, you cannot place a P365 .380 barrel into a P365 9mm slide. The reason is that the .380 barrel hood is actually signficantly wider than the 9mm barrel hood which is completely counter-intuitive since the .380 barrel itself has a narrower diameter.

And, in case you were wondering, the 9mm barrel will not fit inside the .380 slide either.

The .380 barrel is on the right of the comparison photo below:

.380 Barrel:

9mm Barrel:

.380 Barrel not fitting inside the 9mm Slide:

April 12, 2022, 09:12 AM

sigfreund

Over the years I have noticed certain design and dimensional differences among SIG slides and barrels that could have been deliberate measures to prevent swapping among models and cartridges. But too, the wider chamber section of the 380 barrel could be because the 380’s slide is thinner in that area to reduce weight without changing the external dimension.