I have been looking for a P320 FCU for a year or so, but they have been too expensive. I see on Crook Broker that 10-round compliant FCU’s are running $250. I am guessing that they won’t work with hicap mags, but I dunno. Does anyone have the scoop on these, or know if they will work with hicaps? Yes, it’s true, an actual SIG pistol question in the SIG pistols section!

Verbiage from the listing THIS FCU IS A 10-RD COMPLIANT MODEL FCU FOR STATES REQUIRING 10-RD MODEL / SERIAL NUMBER REGISTRATION. The photo clearly shows a large number “10“ stamped on the bottom of the FCU.

This message has been edited. Last edited by: GeoJelly,

Since you are just talking about the Fire Control Unit and I assume you have a grip /frame module that it goes in along with slide, barrel and recoil spring.....

as far as I know there is not difference in the fire control units and really can't see how it could be made to use only limited capacity magazines.

The fire control units are all the same regardless of what size magazine the grip module accommodates. There is no such thing as a “10-round compliant” FCU.

quote:

Originally posted by sigfreund:
The fire control units are all the same regardless of what size magazine the grip module accommodates. There is no such thing as a “10-round compliant” FCU.

^^^^
This is correct. The only differences between P320 FCU's is manual safety/non-manual safety (talking 9/40/357 calibers). While a FCU with a manual safety can have it removed, a FCU without one cannot have it added as the machining in the two frames is different (there are companies that will machine the frame to accept the manual safety components).

This is not the case for the P365 FCU where the manual safety can be added or deleted with a small parts change as the base frames are machined the same.

Sounds like something written for a Gunbroker ad.

The standalone 320 FCUs are all one SKU, as far as I can tell.

The ban-state compliant guns (which ship with 10 round mags only) have the suffix -10 at the end of their SKUs.

Additionally, there are MA-compliant guns which have--in addition to 10 round mags--a Masshole. Those specific guns have -MA at the end of their SKUs. The -MA guns are also good to go in the other ban states (like CO or MD).

Maaaaaaybe those -10 suffix guns have "10" stamped on their FCUs? Never even laid eyes on one of those compliant guns, so I've got no way to know.

At any rate, I can't see how you could have a specific FCU that only allows for 10 round mags to be used, on top of the fact that I see no SKU for such a thing.

And shooters from MA come to SIG Academy to train all the time, and the first thing they do is ask to borrow standard capacity mags, so regular mags clearly work in their ban-compliant guns.

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As usual, SigFreund is correct. I will post info that I think you will find helpful, and I ask SigFreund to correct anything I have wrong.

I own a P320 with Sig's Full, Compact, Sub-Compact Grip Modules and Wilson Combat's Full and Compact Grip Modules.

I've read there are over 40 different configurations you can assemble with the P320. However, there are 3 basic grip sizes which are from smallest to largest: Sub-Compact, Compact, and Carry/Full size.

Because you are asking about the P320's Magazine, I grouped the Carry with the Full size because the length of these Grip Module which houses the Magazine are the same length and their Magazines are interchangeable.

Most often, the P320's are grouped by the Barrell size resulting in the Compact/Carry placed together because they have the same Barrel length.

You can insert a longer Magazine into a Grip Module that has a shorter grip length.

I've shot Full size Magazines in my Sub-Compact Grip Module. In fact, it feels like I have slightly more control over recoil and next shot follow up because of the additional space for my pinky finger.

I expect CCW holders carrying a Sub-Compact could carry a flush Sub-Compact Magazine but carry a 17 round Magazine intended for the Full size Grip Module as their backup.

Getting back to your question, these stats will help, but I've only listed the Magazine capacity that I am aware of. There are certainly more than what I have listed, but when you search for availability keep the Grip Module size in mind.

Sub-Compact overall height is 119mm/4.7" with a 3.6" Barrel:
Magazine capacity in 9mm are 10 or 12 rounds.
In .40/357sig ~ 10 rounds.

Compact overall height is 135mm/5.3" with a 3.9" Barrel:
Magazine capacity in 9mm are 10 or 15 rounds.
In .40/357sig ~ 10 or 13 rounds.

Carry/Full size overall height is 140mm/5.5" with the Carry having a 3.9" Barrell while the Full size uses a 4.7" Barrel:
Magazine capacity in 9mm are 10, 17, or 21 rounds.
.40/357sig ~ 10, 14, or 18 rounds.

The other Magazine item P320 owners need to be aware of is the original plastic Magazine Base Plate will not fit the updated Grip Module without replacing the plastic Magazine Base Plate or a little grinding on the "wings".

Osage County Guns (those guys are awesome!) posted a blog back in 2015 on this subject. Here is a link if you want more info...
www.OsageCountyGuns.com/blog/p320-naming-scheme-causing-headaches.html
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Thank you Gents - finally created an imgbb account - Hope this works:



Picked up an M18 last year but have been using the FCU on a 320 Compact upper. The M18 is just too big for me, and the M18 conversion kit alone without the FCU still isn’t worth so much around here

SIG has long put various numbers on certain pistol parts such as slides. I suspect it is a way of identifying what machinery they were made on, or perhaps for other reasons such as when they were produced.

I just checked four different P320 receivers, including one of the gold-colored “custom” FCUs that were sold separately for assembling one’s own combination of slide and grip module. The large numbers on my receivers where your picture shows 10 were 4, 9, and 14, except for my oldest gun’s and it has no large number there at all.

I can assure you that no P320 is designed to function with magazines having only four or nine round capacities. The standard magazine for a full size 357 SIG or 40 S&W pistol does have a 14 round capacity, but the gun whose receiver is marked 14 was originally chambered for 9mm, and it holds 17 round and larger 9mm magazines just fine.

In fact, of course, the fire control unit of a P320 has no way of “knowing” what capacity magazine is being used with it. The FCU interacts with the cartridges as they’re fed from the magazine for chambering and knows nothing about the length of the mag or whether it might have the little indentations that limit the capacity to 10 rounds—which is the only thing that’s different about the limited capacity mags from the unneutered versions. That’s why I can use a full size mag in a Compact grip module even though it extends out the bottom.

In short, whoever wrote that ad copy simply had no idea what he was talking about, and that is hardly uncommon even among people who should know better. To be entertained, if not dismayed, hang out at a gun shop sometime and listen to what the clerks tell customers.

Hope all that is of some help.

Added: If someone is selling P320 FCUs for $250, I might be interested myself.
Do you have a link?
(Please note: This is NOT a SIGforum WTB ad.)

Just do a search on "320 FCU" at Gunbroker and you'll find a handful of them with buy now prices under $300.

Yes, but not any (I could find) to use with my 10-round magazines and for $250.

There were at least 3 I saw under $250. I am assuming that the "10 round compliant" models are actually FCU's that come from pistols that shipped with 10 round magazines. From SKUs that have the -10 appended at the end, 320F-9-B-10 as opposed to 320F-9-B.

This message has been edited. Last edited by: Paten,

So I looked on Gunbroker a little deeper and there is some shop selling the parted out bottom halves of M17's, FCU, grip module and the one 17 round and two 21 round magazines, for a $299.99 buy now price. They have 5 of them. I don't need one but I don't know if I can resist that price.

^^^^
I bought one of those last week. I had been wanting to get an FCU for a project but I wanted the manual safety. The 3 mags and grip would cost around $180 alone so for the price I thought it was a deal. I have an M18 so I can use the spare mags.

The one I got was an M18 bottom half.