Good Afternoon from Florida,
I just purchased a 320 XCompact. I ordered an extra 15 round mag from the Sig Website. Well...they sent me a 17 round 320 mag. I loaded the mag....tried to manually rack it to chamber the round, and the slide will not go back. However....if I insert the mag with the slide already locked to the rear, the round will chamber using the slide release. The mag is SUPER tight. Can barely squeeze in that 17th round. I’ve read where this mag should work. It’s a 320 mag....has “ Sig” on the baseplate and not Sig Sauer. Is this just a matter of this mag needing to be broken in? It will rack with 16 to rounds, but not with that 17th. Any feedback appreciated.

First of all, good choice on the firearm.

The magazine may be a little tough to load until it's been loaded and unloaded a few times. It helps to use an "uplula" mag loader, especially if you're going to be loading it very much. Your thumbs will thank you.

The 17 round magazine, as you can tell, protrudes a little past the bottom of the grip. If you insert the magazine with the slide locked back, you can over-inert the magazine. The ejector is an integral part of the fire control unit (the removable trigger group assembly). You can over-insert the magazine and bend that ejector. If that happens, the entire FCU assembly must be replaced, as the ejector isn't separately replaceable, and it can't be fixed.

I've never been this happen, but apparently some have. One solution is to not run the 17 round magazine into the pistol unless the slide is forward. Another is to carefully insert it and ensure it locks in place, and doesn't over-insert, when the slide is locked back.

Until the mag spring breaks in a bit, you can do 16 rounds in the magazine to make seating the mag in the pistol a bit easier. The mag shoudln't be tight at all. It may offer resistance from the top round in the magazine...which is different than a magazine which doesn't fit well in a mag well. All P320 mags should slide in and out of the mag well just fine. If you're running into a little resistance seating the mag, that's a tight spring and a loaded mag. You can make it a little easier to seat by loading less rounds, or just exercise the mag springs some. I find that loading them and letting them sit for a time helps. Some claim this is not true, but I've always found it to be true, in nearly every firearm I've ever owned, including a number of P320's.

As for your slide being difficult to cycle with a loaded magazine in place, it will get easier with time. It will also improve somewhat with grease on the rails and in the rail slots. The shorter subcompact slide (the xcompact is a subcompact with a compact frame...the name is confusing) may be a little harder to cycle at first. After you've shot it a little and the springs have had a few cycles, it will be easier.

Thank you for the reply. Yeah....I’m not forcing the 17th round. It racks fine with 16. Interesting about the over insertion of the mag with it locked to the rear. Makes sense though. I carried a 229 for 25 years as an LEO, so I’m still partial to a heavy metal DA/SA Sig. I have 365, but been looking for an XCompact for probably close to eight months or so. Finally got it this week. Weird how I ordered the 15 rd Mag from Sig, the SKU on the box is even for a 15 round, but it was a 17 in the box.

I carry 17 round magazines for the Compact and X-compact, as spares, with a 15 round magazine in the pistol.

If you're at slide lock and insert a fresh magazine, you'd really have to ram it home to bend that extractor. It would need to drive past the mag catch to do it. I don't get too rambunctious about seating a magazine, though with a full magazine, sometimes it does take a good slap to seat the mag, especially on newer springs.

I've been caught sideways a couple of times at matches, with a mag that I thought I'd seated, which subsequently fell out of the pistol. My fault. I watched my son do it, and I imagine the look on my face when it happened to me, was about the same.

To my mind, the x-grip modules feel like lightweight P-series pistols.

If you try the Wilson grip module, it has a different feel. I quite like it. They're inexpensive enough they're worth trying or keeping handy. They do make a 15-round grip module now that fits the x-compact.

If you end up getting 15 round magazines second hand or even NOS, makes sure they have the updated base plate. The older ones won’t fit the x grip without modification.

Also, makes sure you get actual compact magazines, there are some round limited full size mags out there, but sellers often times don’t know what they have.

I bought these off the Sig website. Even spoke to a Sig rep to make sure I was buying the correct mags. They just sent me the 17 round instead of the 15 round.