BREAKING! EXCLUSIVE: Sig Sauer Announces .25 Auto Conversion for MPX

Sig is releasing its first conversion kit for the MPX, and they picked an unexpected caliber.

The wait is finally over.

After years of customer requests, Sig Sauer has announced the imminent release of a .25 Auto conversion kit for their world-famous MPX platform.

“At Sig Sauer, we’re always looking for ways to maintain our position as a leader in this industry,” a Sig Sauer spokesperson told GunsAmerica in an exclusive interview. “That’s exactly what we’re doing with this next evolution of our MPX platform. The .25 Auto has been underappreciated for years, and now it’s getting its day in the sun.”

The spokesperson pointed out that the .25 Auto has a feather-light recoil, and its small size makes it easier to pack than its bigger brothers. Plus, it’s still available during the ammo shortage, and anti-gun politicians are unlikely to ban it.

“It’s the perfect cartridge for the apocalypse,” the Sig spokesperson said. “We’re amazed we didn’t think of this earlier.”

The centerfire cartridge can be reloaded, but Sig Ammunition will also be ramping up production of the .25 Auto and expect to be able to exceed demand.

Conversion kits will include a .25 Auto barrel, bolt, magazine, and recoil springs. Converting to the .25 Auto will be a simple matter of swapping all the included parts and loading up the 50-round magazine.

Sig has yet to release an official MSPR, but sources who spoke on condition of anonymity estimated the kits would retail for around $1,000.

“The .25 Auto was designed by John Browning, who was a total boss,” Sig said in a press release. “Browning developed the centerfire cartridge to fit in a micro self-defense handgun, but we thought, ‘Why not go bigger?’ The MPX is the ultimate self-defense firearm, which makes it a perfect pair with the .25 Auto.”

Cooking along at 814 feet-per-second (fps), the .25 Auto delivers a 46-grain projectile with whopping 68 foot-pounds (ft.-lbs.) of energy at the muzzle and maintains a flat trajectory out to all legal self-defense distances. If that doesn’t sound impressive, consider this: a .22 Long Rifle delivers about 128 ft.-lbs. of energy at the muzzle, making the .25 Auto pretty close to as powerful as the legendary double-deuce.

Plus, with a proprietary 50-round magazine standard in every conversion kit, users can throw a lot of lead downrange in a hurry.

“Everyone these days is so obsessed with ‘knock-down power,’ with bigger bullets moving faster,” the Sig spokesperson told us. “But what about smaller bullets moving slower? With the .25 Auto conversion kit, users can send 50 tiny bullets down range like a swarm of angry mosquitoes. Bad guys won’t know what hit them. Literally.”

Conversion kits aren’t currently available for purchase, but considering the company’s reputation for the timely delivery of new products, we expect the first shipments to be arriving at gun stores soon.

If you haven’t already purchased an MPX, Sig offers a variety of configurations to fit your pistol-caliber carbine needs. Chambered exclusively in 9mm (until today!), these firearms feature internal recoil systems, folding stocks, Timney triggers, reliable semi-auto actions, and 30-round magazines.

Levi Sim gave high marks to the ultra-compact Copperhead model in his full review, and Jeff Cramblit called the MPX the “king of the PCC’s” in his write-up. The new MPX K features a Timney trigger, a threaded barrel, and an M-Lok handguard, and True Pearce got a chance to test it out at the 2020 SHOT Show.

Click here to check out all MPX models.

About the author: Jordan Michaels has been reviewing firearm-related products for over four years and enjoying them for much longer. With family in Canada, he’s seen first hand how quickly the right to self-defense can be stripped from law-abiding citizens. He escaped that statist paradise at a young age, married a sixth-generation Texan, and currently lives in Waco. Follow him on Instagram @bornforgoodluck and email him at

{ 22 comments… add one }
  • Scott April 7, 2021, 6:13 am

    Last time I checked, those energy numbers are for a 22LR in a rifle and a 25ACP in a pistol with a 2 inch barrel.

  • dean April 6, 2021, 6:42 pm

    .25 ACP? Get serious!! Try 7.62x.25–now THERE ‘s a cartridge to consider!!

  • Jesse Tiede April 5, 2021, 8:18 pm

    I don’t buy that bit about the .25 being “almost” as effective as the “double deuce, when the .22 has fully twice the muzzle energy as the .25! I never understood why James Bond was happy about having a “.25 calibre, 007” (From Russia With Love) Survival Rifle, when he could have had a .22, the original caliber the rifle came in, as well as having significantly better choices in obtaining ammunition for it! After all, why settle for hitting a guy in the jaw (.25ACP) when you could kick him in the nuts, instead?

  • August Bender April 5, 2021, 5:21 pm

    This has to be an April Fool joke. I cannot imagine who would want this gun chambered in .25 Auto, much less pay $1,000 for a conversion kit.

  • MO April 5, 2021, 5:04 pm

    I understand the .25 cap have it’s issues but which one of you’ll want to stand in front of the working end and be shot with it?!! I’m just wondering.

  • John April 5, 2021, 3:16 pm

    But why??

  • Leonard S. April 5, 2021, 2:04 pm

    Several years back, I saw a man dig 4 rounds of .25 ACP out of his chest. The wounds had healed over, but he opened them and squeezed them out of his chest. He had been in a barfight and did not know he was shot until he got home and his wife told him. He never went to the hospital.
    This same guy died when he fell off a roof. He owned a roofing company. You would think he would no better.
    Anybody who uses a .25 for self-defense can’t be serious about guns. I used to date a cop. She carried a .25 Baretta (P-25) as an off-duty gun. She had no idea about guns.

  • dave brown April 5, 2021, 2:01 pm

    I actually have used .380 for about 40 years in an old Rem M41 if I remember correctly, and I have used it in a bunch of the so-called new generation of pocket pistols including a BG380 and a Mini Desert Ealge 380, and yes it works. I have used .32acp in a few old Berettas and Savage’s and worked up a nice SD round for my NNA mini, and it works. I actually enjoy a .40S&W or the good old .357 in small guns a lot more. I have a collection of .22lr pocket pistols including Sterlings, and Wilkinson Serry’s, and or course they are fine. Now I always wanted a .25 Baby Browning, but I settled on a mini Llama in .25 which is The Bomb, but rare enough and low on power for a pocket carry. If I want to go small I have an NNA mini 22lr, yet the Llama or Baby Browning would be a better choice as the NNA mini is signal action.

    As for this SIG idea, I just don’t Get It, Now if they did what Mac did and do it in .380 I would Get It. Yet Good Luck and each to there own.

  • NJ April 5, 2021, 12:24 pm

    The fact that you guys may vote, raise children, own guns….and still fall for this…has me concerned for the future of America.

  • David Howard April 5, 2021, 12:17 pm

    Bunch of butt-hurt little girls responding to this article.

    …can you say, “April Fools?”

  • area 52 April 5, 2021, 11:37 am

    Who at SIG thought of this; the same geniuses who were responsible for the SIG556? 25 caliber ammo always cost a small fortune and was and still is extremely hard to find.

  • Vlad Tepes April 5, 2021, 10:56 am

    I have seen a lot of stupid things invented but this really takes the cake. The guy that came up with this idea should be fired at Sig. It was a money loser before the first kit rolled off the assembly line.

  • Shawn April 5, 2021, 10:36 am

    It does not matter how sophisticated the platform, the platform is just the launcher, and it doesn’t increase the effectiveness or terminal performance of the cartridge being fired. And since when is 68 foot pounds “pretty close to as powerful” as 128 foot pounds? And this gem, “what about smaller bullets moving slower” which is apparently a quote from an over-enthusiastic salesman at SIG Sauer. Unbelievable.

  • "Doc" Graham April 5, 2021, 9:44 am

    Seriously?? A “whopping” 68 ft-lbs of energy? That is 1/2 of a 22 LR and also shoots half as flat. The next time I want to send a swarm of mosquitos towards a meth-crazed attacker, I will consider the $1000 .25 cal MPX. This has to be an Aprils Fool one, right????

  • AK April 5, 2021, 9:24 am

    “….after years of requests…”

    Seriously? is there *any* 25 ACP offered on the market anymore?

  • Big Jim April 5, 2021, 9:06 am

    This has a niche, it depends where you are, entering an aircraft with civilians on board? Backyard pest control, training new shooters. Probably not for hikers hoping to fend off a bear.

  • Elmer Fudd April 5, 2021, 8:31 am

    Finally, a cost effective way to kill squirrels in my yard. My MPX is annoying my neighbors.

    How many uses will I get out out of my SIG SRD22 suppressor when I flex this?

    Seriously, sounds like fun other than .25 costing 3x more than 9mm.

  • Danangdoc April 5, 2021, 7:59 am

    James Bond aside, I’m not sure I want to trust my life to a .25. Oh, this is a joke. April Fools Day?

  • Wilko April 5, 2021, 7:46 am

    I feel it is hard to “under appreciate” the .25 acp. If I had to be shot, but could pick the round, the .25 acp would be my hands down choice. A famous quote, by a man threatened with a .25 mouse gun was, “If you shoot me with that, and I find out about it, I’m going to be pissed.”

  • BigC April 5, 2021, 7:42 am

    Most ridiculous thing I’ve ever seen, an overpriced “toy” that fires a vastly overpriced, ineffective round! Maybe, I could see it in .380 but .25, really?

  • Charles Armentrout April 5, 2021, 7:00 am

    The main advantage of a 25 ***in a quality firearm*** has always been greater reliability over rimfire. Ball ammo offers roughly 12 in of penetration. How many 12 in deep holes will it take for you to say no mas? Very interesting indeed.

  • gary holfstra April 2, 2021, 8:53 am

    Everyone must get one of these, they’re awesome! Fly problem? Swat them with a dose of .25! Cat jumping on the counters? A little .25 swat will get ’em down. Irritating pimple that you can’t pop? The .25 should be able to take care of that too! All around useful home entertainment system!

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