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This email blast was issued by SIG SAUER today:

SIG SAUER – MCX Mandatory Carriage Assembly Replacement Program

SIG SAUER is conducting a mandatory replacement of the carriage assembly in SIG MCX rifles. SIG has found through extensive factory testing that in extremely rare instances, not reported in the field and extremely difficult to replicate, a condition may exist causing an unintended discharge. Failure to follow the loading procedures and basic rules of safe firearms handling outlined in the user’s manual has the potential to cause serious bodily harm or death. Although this has only been witnessed in 300 blackout, SIG has decided to upgrade all MCX models since the MCX is a modular platform and we want to ensure the quality and reliability of all products we manufacture.

Stop use of firearm immediately, and visit the SIG SAUER website listed below as soon as possible to register your firearm, initiate the process and view a video explaining how to change out your carriage assembly. SIG will send you a prepaid box to return your complete carriage assembly to the factory. A new assembly, designed with the firing pin locking mechanism, will be shipped out to you within 5-7 working days of the receipt of your parts at no cost to you. Please note total in transit times will vary based on geographic locations. SIG will also send you a $50 gift voucher for any inconvenience this may have caused. This upgraded carriage assembly addresses this potential issue while enhancing the performance and longevity of your rifle. You may also contact SIG SAUER customer service at the number below with any questions if needed.

SIG SAUER is committed to addressing this issue in an expedited manner, and appreciates your support.

Firearm Registration –

For Customer Service – 603-610-3000: OPTION 1 

For Instructional Video –
*Serial numbers 63C000044 – 63C003702 – Contact SIG Customer Service for instructions.

*If you have replaced your trigger group with an aftermarket trigger please contact SIG Customer Service for instructions.

*SIG SAUER Dealers should call designated Commercial Sales Support Representative.

*Any MCX rifle with a serial number ending in 25000 or higher is exempt from this program.

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  1. Eh the old version uses the same system on every other ar-15, so what’s the problem? I’ve heard the recoil spring sometimes binds and causes failures. and the new bolt has a Non-removable firing pin retaining pin(So how do you clean/replace it?).

    • I had the same thought as I lo9oked at the diagrams. It didn’t make any sense, as this seems (so I’ve heard) to be a source of failure in AR style rifles.

    • “… the new bolt has a Non-removable firing pin retaining pin(So how do you clean/replace it?)…”

      My guess is that for cleaning you’d just pull the captive firing pin retaining pin (just like you do with the captive front and rear receiver pins on an AR) and for replacement you drive out the roll pin which secures the firing pin retaining pin (as pictured in the illustration). “Non-removable” doesn’t necessarily mean the same thing as ‘welded in place’.

      • Folks who have called SIG today are reporting that it is indeed as you described, “captive” not “immobile” (welded/pinned/peened), if this is the case i’m quite a bit less upset about it.

  2. Well, I guess my skepticism was well merited, once again with Sig… they ‘jumped the gun’.

    Yes, I have a snarky little smile. For once, I didn’t have to be the early adopter (re: beta tester) having to deal with yet another friggin RMA.

    I knew something was up when these quickly stopped being shipped after the initial run had all kindsa problems. I wanted so much for a 300 blk piston shortie to be a reality, but have since given up that ghost, and am quite happy with my AAC MPW 9. There’s a reason why LWRC made their 300 Blk shortie their first DI gun ever!

      • I’m not familiar with slam fire. Would that imply that when dropping the bolt on a new magazine you get an unintentional discharge?

    • Exactly as Norinco says. Slam fire. The firing pin is free floating (just like an SKS, AR15s, M1 Carbine, Garands, M1A, and many others). This means when you pull back the charging handle on an AR15 and let it go, the firing pin smacks into the primer each time. This usually isn’t enough impact to ignite. Which is why you should always keep your muzzle pointed in a safe direction. Some primers are softer than others. I reload and use harder primers for guns I know that have free floating firing pins. Regardless, it is a very rare occurrence.

    • As an owner of many West German marked guns, they can’t even claim that either, at least not in the present tense.

      • Haters gonna hate.

        Personally I love the videos and the (so implied) verbosity. And I was right, it was the same type of failure.

  3. This is a trap!

    They want us to register our rifles? Screw you! Make a bad rifle, fine, replace it, but register? Haha Obama, you’re not as smart as you think you are!

    • Did you read it? You are simply sending in your carrier group not the whole rifle. Most manufacturers ask you to register your serial number for warranty. Calm down

  4. So…I just called and was told most aftermarket triggers would not work with the new bolt carriage. They are going to give everyone that has aftermarket triggers new Geissele SSAs free of charge. The downside is you have to send the complete rifle in.
    It sucks because I won’t have my rifle, but my trigger was a Hyperfire HDT so I think the SSA is an upgrade.

  5. So, the replacement ensures that you can no longer disassemble your rifle? No thanks. “Non-removable firing pin retainer” and “Non-removable spring plate” are unacceptable. Especially for suppressor users.

    • ouch. just seeing that. yeah, that really blows. I guess I should couch my previous wise ass comment a bit, knowing that people really got burnt on this one. I’ve been there many times. It’s not fun, Would be nice if maybe they give everyone the option of a full refund the way Eotech did.

    • Word is starting to trickle out now from people who called Sig that this isn’t the case.

      They mis-described it there as “non-removable”; it’s not peened in, but it is “retained” or “Captive”, meaning you can slide it out of the way, (think AR takedown pins) but you can’t remove it from the carrier itself.

      They’re closed now, but I’ll call about mine tomorrow and see if that is indeed the case, and update here.

    • Captured is not the same as immobile. look up the bolt on the Daniel Defense dd5 308. Similar design for the captured retaining pin.

  6. I’ve seen one .300BLK setup, Military Arms Channel, can’t even find where they sale the conversion. My guess only group that would have run into this and got Sig’s attention is a SOCOM command. I’ve wanted almost 4 months for my MCX, had an aftermarket trigger for 3 months waiting on it to show up. This explains the long wait time. Here is my shocked face 😐 that they are really good at letting customers beta test their products, P320, ooops our bad, the 9mm or .40SW fire control group won’t work in the .45ACP, MPX, hey we didn’t make the ejection port big enough for .40 or .45ACP so we’ve made a Gen 2, you fools that have a Gen 1, THANKS FOR YOUR MONEY, now MCX.

    I called the number, pressed 2…… Are you a dealer? No, let me send you over to Customer Service, 12 mins on hold so far………

    Just received a new email, says use option 1 now….. They can’t even get an email right.

    • “My guess only group that would have run into this and got Sig’s attention is a SOCOM command”
      I assume you just mean SOCOM, but even so, why would they have run into this issue with a round they dont use?

      • Round they don’t use? The only two calibers that I know of for the MCX are 300 black and 5.56. They share the same parent case, no? It would only be natural to assume that what happens in the carrier of a 5.56 could happen in the carrier of a 300 (since they should be the same dimensionally).

  7. That’s why I gave up on Sig Sauer about five years ago I had some complete failures with my P238 380 automatic Colt Mustang clone. I’ve seen so many sig sauer’s that are shot come in with broken Springs and just cheap little parts that they’ve used that keep the weapon from actually functioning when they break and I’m talking about $0.10 little springs that they could have spent a little bit more money and had a spring that would last forever instead they go the cheap route as usual with six hour. They are living off the name that’s our rifle Works in Germany created. If you get a chance to own a Sig Sauer buy one that was made in Germany not and New Hampshire.

  8. SIG better stick with purple and pink 380 and 22cal pistols, their vaunted re design of a proven platform is a bust.

  9. Has anyone yet received their new bolt carrier group? I called almost immediately and have not received return box. Yet Sig is advising to immediately stop using MCX, grr. Shipping boxes and replacement carrier groups along with credit vouchers should be faster and smoother than this!

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