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Patrick writes:

Hi, you guys are going to review the new Sig MCX once you can get ahold of one, right? According to Sig’s Facebook/Instagram they just started shipping them today. I so want to buy one of these but your blessing would be one of my requirements. 😉

To paraphrase the Pope: who am I to disagree? We asked, they provided. And now one of the first full production SIG SAUER MCX rifles is sitting in my trunk waiting to be reviewed. I’ve had some time to play with the gun at SIG SAUER’s facility and SHOT range day. So far I can say . . .

I’m very, very happy with the end result. I was worried that something would be lost in translation, as the MCX went from an engineering experiment to a SpecOps full-auto toy and finally to a firearm that you’ll be able to walk into your local gun shop, plunk down your hard earned cash, and walk out the proud new owner of a Title 1 version of the mythical beast. A few questions remained unanswered . . .

We’ve never really gotten a good objective assessment of the accuracy of the firearm. Shooting it into the berm and at close range paper targets is one thing (and it does wonderfully in that realm). The true test of the gun: can it hold its own when you directly compare a 5-round group from the MCX with a 5-round group from a similarly priced firearm. I’ve been a little disappointed in the accuracy of some of SIG’s latest concoctions. Hopefully they’ve ironed-out the kinks at the barrel shop and we’ll see some tighter groups this time around.


The other concern: are the ergonomics are up to par? The MCX uses a new skeletonized stock. It looks dead sexy, but I haven’t had enough time behind the gun to really evaluate its practical aspects. I’m concerned that she’ll be a bit front-heavy during extended use sessions due to the lack of junk in the trunk. The pencil profile barrel might restore balance to the force. As an SBR it works, but we’ve never really seen a 16-inch version. So we’ll see. Full review to follow.

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  1. One thing worth noting if this take a large amount of bolt on AR parts is that a BAD lever isn’t compatible with the mag release. I have one on my (non SIG) AR, and love it. They are hard to come by though.

    • The BAD lever has to be slightly modified. Some material has to be removed from the piece of lever that goes between the bolt catch and receiver plus you have to slightly bend it for fit. There’s video on how to do it. Pretty easy to do for any DIY’ers

    • I wonder if the ambi part of the mag release can be taken off. I for one have zero need for a mag drop on the left side of the well, and if it’s in the way I’ll have no problem with popping that sucker off.

  2. “Introducing the SiG MCX™. Engineered for 300BLK. Built from the ground up to be silenced, light and short. A breakthrough in modularity. The result of years of toil and sweat, the SiG MCX is proof that the dawn of a new era doesn’t happen overnight.”

  3. I fondled one of these a couple of weeks ago at the LGS.

    In regards to the skeletonized stock, I specifically remember thinking at the time about how sturdy and heavy it felt. It felt heavier than a typical AR-15 plastic stock. The locking mechanism was also interesting, it doesn’t use a button but instead a unique friction fit that requires you give it a stout upward bump to fold inwards.

    Overall, it was pretty cool, I like it a lot.

  4. Please stop reviewing guns.

    My safe is already full and the wife *will* notice if another one (safe or gun) shows up.

    Unless I put it in the back closet, maybe… Hmmm….

    • “Please stop reviewing guns.

      My safe is already full and the wife *will* notice if another one (safe or gun) shows up. ”

      Another satisfied TTAG customer…


    • I hear that once you get past the first half-dozen or so black rifles, women start having trouble telling one from another, especially if you mount things on the rails and change up what’s attached to what every so often.

    • In picturing a Looney toons style attempt to close the safe door with just one more gun inside it while the safe door bites and bulges under the strain, resulting in the inevitable yet still hilarious explosion of contents leaving you sitting in a pile of guns.

  5. I had the opportunity to fire one of these at a local range with sub-sonic rounds.

    I took a pass, and continued firing my own P938, as it was;

    A> Brand new
    B> I didn’t know the guy, just another kind soul like I usually see at the range.
    C> I didn’t want to somehow break the thing!

    I also figured it would be front heavy, as I did heft it, but it only felt slightly that way.

    I just wish I had the cash, as I do with a lot of firearms, but preliminary indications were good, and it
    fired well, when he shot it…

    • I consider it rude not to fire a gun that’s offered to you – both to the owner and to yourself. Don’t be rude, shoot the darn thing. ?

  6. Great platform in every caliber, even 7.62×51 (kicks like a mule). My one and only complaint is the stock that it ships with is the most uncomfortable factory stock I have ever shot. I like how its a folder but man, what a bruiser. When I get mine I am buying a KAK buffer tube adapter, buffer tube folding adapter and some kind of nice AR stock

  7. That stock looks very uncomfortable, and also very flimsy…

    Also, given the numerous severe problems with the recent SIG rifle offerings (556R and 556xi), I would want a very thorough reliability testing of this thing before I’d trust it.

  8. One day I’ll trust Sig to produce e something decent again. It’ll be a long time before I spend another 4 figures on that company after the 556xi experience I had.

    • I leaning towards agreeing with you. I sent my MCX in .300 BLK configuration back to Sig since the second time I went to the range it started auto firing. They’ve had it since the beginning of October, 2015, and I’m still waiting to get it back.

  9. I bought one. The weight is fantastic! I love everything about it. The stock is really nice and solid. Locks up securely. I find it comfortable, but I am also used to shooting underfolder AKs and worse wire side folders. The handguard is incredibly light. They advertise the rifle at 6lbs, and it feels like it. I’ve been very pleased. I can’t wait for Sig to come out with their accessories, and caliber conversions. It’s really exciting!

  10. I handled one of these at my LGS. When I first picked it up I had seen the skeleton stock and the large hand guard in the front and assumed it would be fairly heavy with most of the weight out in the front. To my surprise the rifle was very light and way more balanced than I expected. The hand guard is much lighter than I would have thought it was. Looks cool, I’m sure it runs great, but I’m not spending my hard earned cash on it (unless maybe I get it in a suppressed 300 blk SBR)

  11. Any chance you can try the upper on an AR-15 or even better, an M-16, since one of the big selling points is that the upper and lower are compatible with AR-15/M16 uppers/lowers.

  12. Well I’m definitely not a gun expert but after looking at the website spec’s I can say the trigger sucks and would need to be replaced before first use for any kind of true accuracy.

    The angled stock makes me wonder if its prone to muzzle rise or will cause problems when fitting it to your shoulder. The pencil then barrel looks like its going to be prone to warpage when it warms up.

  13. I have a MCX in 5.56 and it is wonderful … With 75 gr. H Match ammo it shoots right at MOA @ 100 yds. .. I’ve only put 300 rounds thru it so far , and can tell you the 1:7 twist doesn’t like 55 gr. Cheap (plinking ) Factory ammo for tight groupings ..
    Other than that , ITS GREAT !

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