[Malum Prohibitum]

it has no been adopted by the US Army as their official pistol.

Did you mean to say it has YES been adopted by the US Army as their official pistol?

 

[Malum Prohibitum]

Love it! Best caliber out there. Go with Underwood ammo. For some reason, most ammo makers water down their 357 SIG offeringsâ€"not Underwood. The other thing about 357 SIG is you can switch to 40S&W with a simple barrel swap for two guns in one. Uses the same magazines and everything. Sig even marks their mags "357SIG / 40S&W".

Isn't the whole modular concept to this pistol meaning you can also convert it to 9mm and .45 ACP, in addition to the two calibers you listed?

 

[Malum Prohibitum]

Why don't they make a 10mm? Frame can't take it?

 

[Malum Prohibitum]

Why aren't the FDE military versions out for sale yet?

 

[Malum Prohibitum]

Why is the full size .45 magazine limited to 10 rounds when the 9mm is 21 rounds? .40 and .357 are 14 rounds.

 

[Malum Prohibitum]

Frame is too short front to back to handle 10mm.

This. The COAL for 9mm, 40 and 357 are all about the same. 45 and 10mm are about the same COAL.

Wait, isn't the .45 a part of this modular gun lineup? If so, then the COAL issue is not the issue.

 

[Malum Prohibitum]

https://www.gunsamerica.com/blog/sig-sauer-p320-grows-up-to-45-acp-review/
From the comments:

Clarification on the 320 and if it can be converted back and fourth from a 45 to a 9mm. I just took a few classes at the Sig Sauer Academy and fell in love with the 320 after firing it at their facility. I had the same questions about converting and I was told directly from the rep at the pro-shop on the Sig Sauer campus that yet it can, with a catch. You must purchase a 320 chambered in 45 first and then you can purchase any of the conversion kits available to convert it (say to 9mm). You can't do this the other way around. I purchased a P320C chambered in 45 and plan to convert it to 9mm (full size). I hope this helps as I am sure that the dealers may not have this information and to get the most bang for your buck (options speaking) purchase the 45 first and then convert.

 

[Malum Prohibitum]

On the Sig web site, the full size 9mm and .45 are the same dimensions, weight, and barrel length, but apparently there is this issue with the grip size and the hole for the magazine.

Still, then, it seems some crafty engineer should be able to put together a 10mm kit for the .45 P320, and then you can have 5 calibers in one gun, if desired.

 

[Malum Prohibitum]

Just a followup to my original post.

I took my P320C .45, P320F 40 S&W and P320CP 9mm to the range yesterday. I installed the .45 FCU in both the F and CP pistols and fired 50+ rounds through each. The .45 FCU fed, fired and ejected the .40 S&W and 9mm ammo without any problems. It appears I've answered my own question. the .45 FCU is downward compatible with the smaller calibers.

http://sigtalk.com/p250-p320-modula...ct-45-fcu-9mm-sub-compact-conversion-kit.html

 

[Malum Prohibitum]

http://sigtalk.com/p250-p320-modular-pistols/44956-will-9mm-exchange-fit-p320in-45-pistol-2.html

Quick answer I got from Sig is yes! I live just outside of Exeter, NH and just took 3 classes at the Sig Sauer Academy. I fell in love with the 320 while shooting it at their range and asked this exact question at the pro-shop on the Sig Sauer Campus. I was told that if I purchased the 320 chambered in 45 that I could convert it to a 9mm (or 40, Sig 357) with the conversion kits. I was told by the rep that this is the only way you can have it both ways as you can't convert the other way around. I ordered a P320C chambered in 45 as they were out of stock at the pro-shop and they stated they would call me once it was manufactured and shipped from the factory. I will then purchase the 9mm (full size) conversion kit. If there is continued interest I can update this post after receiving and attempting the conversion. I am interested in seeing if it is as reliable converted into 9mm as the one that I shot that was originally set up in this configuration. Hope this helps.

 

[Malum Prohibitum]

I have a 9mm version. It is the gun one of my sons uses for handgun classes. It is full size.

I would buy a 10mm version in a heartbeat.

I like this gun. I like the trigger. I like the accuracy. I like the ergonomics.