Witness the Magic Modular Chassis of the SIG P320: Change Grips, Calibers in a Flash!

With all the winning SIG Sauer has done over the last 18 months with the P320, I feel like here at GunsAmerica despite our extensive coverage of the U.S. Army Contract, the X-Five, the X-Carry, the RX, the LIMA Laser Grip we have forgotten to highlight one great feature.  The P320’s magic modular chassis system.

Caliber X-Change Kits contain everything you need: a complete slide with sights, grip module and a magazine.

A lot of companies have hyped a “modular chassis” handgun system, but most of them fall short. The SIG P320, in my experience, has been the only one that is truly modular in that it is really easy to swap from one frame or caliber to the next. Even with a new gun it takes only about 30 seconds to change out. This week I got my hands on a couple of caliber conversion kits and tested them out.

The “Caliber X-Change Kit,” as it’s officially called, is a product direct from SIG.  The kit includes everything you need: a complete slide with sights, a frame, and a magazine. The best part about this system is that it’s not only good for swapping calibers but for frame sizes as well (compact, subcompact, carry, full size and RX).  You can go from a full-size race gun to a concealed carry pistol in a flash. And recently, SIG added the RX models as an option, which includes the SIG Romeo1 red dot sight.

So, why is this valuable? In my mind, it comes down to versatility.  One gun, which also means one form 4473, gives you numerous options.  I always recommend to new shooters that they start with a full-size pistol chambered in 9mm. That has to do with training dollars and forgiving recoil, nothing to do with 9mm’s effectiveness or lack thereof. I don’t care what the FBI says, I prefer a harder hitting round in a duty gun. And after they did such a bang-up job on the Hillary email-server investigation, maybe you should question what they say too. I will also be the first to admit that it is easier to shoot a full-size gun but easier to carry a compact or subcompact gun.

These conversion kits offer you the ability to train with cheap 9mm in a big boy gun, but in 30 seconds have a compact carry gun chambered in.40 S&W. This also has the added benefit of letting you carry a gun with unworn internals, except the fire control group. With Murphy’s law ever-present for the op order, it’s best to give him the smallest role possible.

The conversion also offers a third benefit. I ordered mine in .40 S&W (my favorite caliber) and .357 SIG. Not to offend the .357 cultists in the audience, but prior to this I wouldn’t be caught dead with a gun in that caliber. Not because I think it won’t perform. Because ammo is scarce and expensive. A quick glance today shows it at double the price of 9mm, and 10 cents per round more than .40 Slow and Weak. But will I take a gun that fires .357 SIG on special occasions? Yes. Yes, I will.

A single gun with multiple calibers also makes a great survivalist gun. Setting aside the grips for a moment, you could plan this a different way. A full-size 9mm gun, plus two slides and one set of spare magazines sets you up for success in a big way (.357 SIG and 40 S&W use the same magazines in the SIG platform.) At a very limited weight addition to your kit, you can shoot almost anything you can lay your hands on. During ammo crunches, strange things happen. I remember in 2013, where I was living at the time, you couldn’t touch .45 ACP, .40 S&W, 9mm, or .380. But .45 GAP was still on the shelf. 357 SIG is more popular than GAP, but still not all that common.

Steps for Swapping

1. Clear the pistol and lock the slide to the rear

2. Remove the slide, no trigger pull necessary.

3. Wiggle out the takedown lever.

4. Remove the firearm control group from the grip module.

5. Build whatever gun you fancy.

X-Change Kits in hand, I headed to the range. This wasn’t so much a test as a verification of a highly probable eventuality. Using the X-Carry grip module, I swapped over to .40 S&W and then .357 SIG. Both ran flawlessly using SIG’s own brand of ammo. And while I am not quite ready to order the die set for 357 SIG, it at least now has my attention. Right now, the conversion kits are only for 9mm/.40S&W/.357 SIG, with no .45 ACP announced. But the paragraph above gave me a great idea. What if SIG released one in. 45 GAP?

SIG’s Caliber X-Change Kit. Retail starts at $407.

Price for the X-ChangeKit starts around $407.  For more information visit SIGSauer.com.

***Shop for a SIG P320 on GunsAmerica***

About the author: Clay Martin is a former Marine and Green Beret, retiring out of 3rd Special Forces Group. He is a multi-decade and -service sniper, as well as 3-Gun competitor and Master ranked shooter in USPSA Production. In addition to writing about guns, he is the author of “Last Son of The War God,” a novel about shooting people that deserve it. You can also follow him on twitter, @offthe_res or his website, Off-The-Reservation.com

{ 12 comments… add one }
  • Steve July 6, 2018, 1:39 pm

    I have the p320 X 5 and the P320 VTAC with all the x change kits and they work flawlessly.

  • Larry Mills July 6, 2018, 9:14 am

    reloading 357 sig can be a pain sometimes with some brass with small flash holes

  • Dave June 27, 2018, 11:56 am

    I am with Clay; I prefer .40SW for EDC. And overall, the price difference between that and 9mm is negligible. As for the new modular pistols being produced these days: great concept all around, especially giving a person the opportunity to have multiple pistol calibers and grip types in one firearm. Obviously Sig is not the only company to do this. But they have put together a nice package for the civilian owners. It also allows a person to have the multiple calibers and grips for less than the cost of a purchasing another firearm of Sig quality. I do own a P226 Legion in 9mm, but only because I wanted the SAO trigger, and at the time the SAO was only available in 9MM and not .40. It is a large and rather heavy pistol, and I would not carry it for EDC. But should we have a zombie apocalypse, or some other nation try to invade us, I would carry it with a +P load, along with my .40. I am a Sig fan and believe they produce some of the finest military and LE weapons on the market. And we civilians get to benefit from these products because most are available to us. The P320 is a prime example: developed specifically to meet military specs and to compete for military contracts and yet it is available to everyone. And best yet, at prices most everyone can afford.

  • wiscogunner June 22, 2018, 11:04 am

    XYZ my friend.

    Thanks for the article. Sig and a few others have a great concept with using one chassis to support multiple calibers. Also, I would like the put a word in now that when Sig comes out with their Gen2 of the P365 and fixes the issues with the firing pin and slide wear, please do a review after 500-1000 rounds of testing. I enjoy your reviews especially when range video is included. Keep up the good work!

  • Kip Babington June 22, 2018, 10:10 am

    Can you actually order these coversion kits and get ’em by (approximately) return mail? I remember an earlier SIG offering with these covertible features. They had great frame-size displays in stores for you to compare grip sizes, but IIRC you could never really get the conversion parts after you bought your original gun.

  • victor jankowski June 22, 2018, 9:20 am

    I have been a gun collector and competitor for over 50 years. I always prefer all steel handguns and could care less about the weight. Therefore, I have stayed away from guns with plastic frames. Recently, I broke my own rule and purchased a Cz Evo Scorpian in 9mm. Love the pistol, but hate the plastic frame. Recently, purchased a pair of Sig Legions. One in 9mm and the other in 45acp. Once again, love the pistols, but not really happy with the alloy frame. I wish the (all steel) Sig Elite was made in 357 Sig, Yes…I do carry all steel guns. Learned to live with the weight. Recently, I almost purchased a Bereta 92 FS. Then I discovered all the plastic parts and got really turned off. I would have to purchase many aftermarket parts, or buy a Wilson. What I really desire is an all steel Sig 226 in 357 for my daily carry gun…

  • Rick Tousignant June 22, 2018, 9:20 am

    I’m the owner of a P320 compact, in 9mm. Can I buy the Sig. exchange kit and turn it into a 9 or 40 Caliber RX Sig? I’d love to have the Romeo sight without having to buy a new gun again.

  • Mark N June 22, 2018, 8:51 am

    If you own the 9mm version of the P320, you do not need to purchase separate exchange kits to convert it to .40 cal and .357 Sig – only one. The two aforementioned exchange kits are identical except for the barrels. Simple solution: purchase the exchange kit of your choice for either the .40 or .357 Sig and then purchase the barrel only for the other caliber. The barrels for the .40 and .357 Sig are interchangeable just as the magazines are for those two calibers. I made my purchases through Sig directly. The number is on their website.

  • Jay June 22, 2018, 7:47 am

    It never fails article after article talking about the 40 or 45 being superior to the 9mm in some way or the other! I see Clay is not immune but understand his choice, it’s what he is use to and probably more familiar with and I agree full well on his questioning the government information. Today’s modern ammunition has closed the gap on many caliber choices. Real world ballistic test, meaning autopsies results, have proven over and over that the size difference between the 9mm,40,45 has very little to do with incapacitation and someone being able to return fire. It has always been and always will be, in the real world, Shot Placement! Carry what you can shoot well under stress!

    • James January 1, 2019, 2:24 am

      I am not sure what autopsy reports you’ve looked at but the most recent study I’ve seen outlined the number of shots vs caliber in shooting deaths. 45 ACP consistently, over and over again required fewer shots (usually one or two) for incapacitation.

  • MathSux June 22, 2018, 7:27 am

    $.36 a round is exactly double the price of 9mm training ammo at Walmart or online from Freedom Ammo. $9 a box(50) vs $18 makes a huge difference in range time.

  • JHR June 22, 2018, 6:31 am

    Recently purchased a Sig 320 RX Carry in 9mm I’ll probably never convert the frame to anything else. The size covers both aspects; a concealable pistol and the accuracy of a full sized pistol.
    I’m constantly amazed at the accuracy of this pistol. It is every bit as accurate as my P-226 Elite at a much lower weight.
    As far as .357 Sig ammo goes it is not any more expensive than any other cartridge, if you shop around. Just picked up 1000 rounds of Speer Lawman for about 36 cents a round. Of course if you are after super duper self defense rounds the price jumps but that applies to all other caliber’s as well.

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