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First Look – USSOCOM’s New Suppressed Upper Receiver Group (SURG) from SIG SAUER

Late last week, the United States Special Operations Command announced they had awarded SIG SAUER a $49 million contract for Suppressed Upper Receiver Groups for the M4A1 weapon.

Here is the first photograph of the SURG in the wild. The SURG components are mounted to a generic AR-style lower receiver.


Based on the SOCOM requirement, SURG includes a 5.56mm NATO upper receiver group (URG) composed of upper receiver, barrel, operating system assembly and bolt/carrier assembly along with a sound suppressor (may be integral with barrel), operators manual and maintenance manual. In addition to the URG itself, candidate systems could include a folding stock if the operating system didn’t require use of the lower receiver extension, buffer and action spring.

As we can see here, SIG went a different direction than most and used an MCX piston driven upper with detachable suppressor and an MCX folding stock. As part of SURG, SOCOM will receive the folding stock and knuckle adapter for use with existing M4A1 lowers. The suppressor is covered with some sort of aramid-based mesh to protect the hand of the operator. When you get to the performance specs below, you’ll understand why this is so significant.

I’m now going to go over some of the requirements for SURG so you can see how SIG (and the other candidates) had to perform to win this solicitation.

SOCOM stipulated that SURG could be no more than 25.5 inches in length but that they preferred a system that was no more than 21.0 inches. The barrel has to be at least 11.5 inches in length and the weapon can’t weigh more than 7.0 pounds, but the preferred weight is just 4.5 pounds. It also needed to be Coyote 498 in color.

The real meat of the requirement is in the suppressor performance. First off, a SURG equipped M4A1 has to be optimized to fire the M855A1 and the MK318 MOD0 / MOD1 cartridges and be able to do so reliably for at least 1200 rounds without lubrication. Obviously, they also didn’t want anything that could vibrate loose. While the suppressor must be rebuildable, only one component of the suppressor has to be serialized but that part had to last the lifetime of an M4A1 lower receiver (125,000 rounds). The rebuildable components need to last at least 15,000 rounds but SOCOM further challenged industry to make them last for 20,000 rounds.

Additionally, a SURG equipped M4A1 shall not exceed 140 dB ten shot average sound pressure level at shooter’s ear during barrel life minimum (15,000 rounds).

In the past I’ve mentioned the so-called SOCOM suppressor torture or stress test. The SURG equipped M4A1 has to withstand at least 6 complete cycles of the firing schedule seen below below using MK318 MOD0 / MOD1 ammunition with SURG allowed cooling to 120°F after each cycle. However, SOCOM was hoping to complete 20 cycles.


The weapon firing MK318 MOD1 for 5 groups of 10 rounds each suppressed, has to average over the 5 groups no more than 1.50 MOA Extreme Spread (ES) beyond the ammunition Lot Acceptance Test (LAT) average ES at 300 yards. Also, it has to maintain a maximum ES Average of 1.50 MOA over LAT using MK318 MOD0 / MOD1 ammunition from 0 to 10,000 rounds fired.

In addition to that stress test, SURG has to prevent operator contact or sustained contact burns from the suppressor (or equivalent) through 1 layer of standard military duty uniform material after firing 210 rounds in 7 minutes at a rate of 1 round every 2 seconds ± 0.2 seconds. A contact burn will be defined as a peak temperature over 160°F in 1 second of contact. A sustained contact burn will be defined as a peak temperature over 160°F in 5 seconds of contact.

These stringent requirements, combining suppression, reliability, accuracy service life, and operator protection were very challenging for industry. It took three tries at bat for the SURG program to finally select a system. In the two earlier attempts, none of the systems could meet all of the program’s objectives. Kudos to SIG for putting together a winning system.


52 Responses to “First Look – USSOCOM’s New Suppressed Upper Receiver Group (SURG) from SIG SAUER”

  1. abp says:

    socom should just replace all their M4s with non-supressed MCX uppers. And hopefully that would trickle down to the big army just like the M4 itself did…

    • What’s wrong with the seemingly forgotten 6.8SPC? Out shoots both 5.56 and 300 Blackout. I use mine for wild hogs at 300+ lbs and whitetail deer with never a followup shot. Yes, the round adds a small increase in weight but do-able on extended movements. Long range accuracy is outstanding and throws a far heavier projectile with a high BC. No experience with the 300 Black so unable to comment.

      • Ryan Snow says:

        The 6.8 spc failed miserably overseas. The cartridge tumbles and keyholes after 150 yards when fired out of a UCIW. Don’t believe the hype

        • Joe a says:

          That’s because production rifles when the 6.8 spc was intoduced we’re not complete rifles now have a diferent chamber spec II and diferent twist rate old 1 in 9 new 1 in 11.25 the improvements really make the round shine I shoot 6.8 right about an inch @ 300 yards no problem 110 gr to 130 gr this is not possible with the old twist rate

      • theDude says:

        A 6mm grendel will outshoot the 6.8 anyday. 6.5mm is what socom is moving too for lighter sniper rifles /semi autos.

    • Joglee says:

      I wonder if that’s not the end goal.

      This is basically a Mk18 replacement and I can see it being a M4 upper replacement. SSD?

      • SSD says:

        As of right now, “it’s just another tool in the toolbox.” However, SOCOM also has a requirement for a .300 Personal defense weapon. Considering the MCX’s ability to swap barrels quickly, this may answer that requirement without a full solicitation. In fact, they purchased a small number of MCX uppers to inform that requirement earlier this year.

        Both SURG and PDW are primarily NSW and MARSOC requirements. USASOC is not participating in either. Instead USASOC is going a different direction to upgrade their M 4A1 uppers. Consequently, I do not believe this will become the new SOCOM upper receiver group.

        • Joglee says:

          Thanks SSD. I’ll keep an eye on this.

          It should be interesting to watch. According to what is claimed the surge essentially doubling parts life of the weapon compared to a CQBR, and at a cheaper price.

          Why keep procuring CQBRs from Crane when you have an option for a better upper?(if it lives up to what’s stated.)

  2. Iceman says:

    Great write-up as always SSD. In looking over your notes did it mention how much usable rail space the gun needed on the L and R side?

  3. d says:

    Part of me was hoping for a really short 300, but this’ll do.

    I wonder what will trickle into the civilian market as a result.

  4. DangerMouse says:

    Man, I hate to be the guy doing the burn testing 😉

  5. Ed says:

    So the requirement was for a short-stroke piston upper or can it also be a DI upper as well?

  6. XM177E2 says:

    SOCOM can just replace all CQBR with this thing now…

  7. SVGC says:

    I’m surprised to see that the stock is the fixed LOP variant and not the adjustable one. I would’ve figured that wouldn’t be an option. Any idea if the suppressor cover itself is removable?

    • Mike says:

      The lower has nothing to do with the contract. ?

      • SVGC says:

        “As part of SURG, SOCOM will receive the folding stock and knuckle adapter for use with existing M4A1 lowers.”

        Thank you for incorrectly correcting me.

        • Jay says:

          Could it have something to do with the weight requirement of the contract? That the fixed LOP stock saves enough weight over the adjustable to help it win the contract or edge out the competition?

          • SVGC says:

            Maybe so. I couldn’t say. It’s something easily changed of course and maybe it still can be IDK. Just wouldn’t have expected to see a fixed LOP.

        • SVGC says:

          Gotcha, thanks. I’m curious to see it and what the OD is and it’s compatibility with a device like the MAWL.

          • Gear Guy says:

            I am a huge fan of the MAWL as well, but it isn’t getting the traction it needs to be procured in heavy numbers by those organizations that have been evaluating it. Plus the next gen PEQ units are pretty nice and have been getting solid reviews by the users testing them.

            • SVGV says:

              I agree, it’s not exactly zooming off wholesale like I really wish it would. I’ve been using the DA for awhile now and there really is nothing like it at this time, even compared to the NGAL or other future units. My curiosity of compatibility is more of a personal interest. The unique design and body of it is cool but it adds another layer of design considerations for a myriad of applications to include weapon systems and observation devices. I’m just curious who is taking it into consideration for any potential future use.

      • Joe_K says:

        The stock however does. Fourth Paragraph down, second sentence.

        “As part of SURG, SOCOM will receive the folding stock and knuckle adapter for use with existing M4A1 lowers.”

      • CAP says:

        You can’t put an MCX upper onto an AR lower without changing out the stock assembly. The adapter that replaces the receiver extension holds the recoil spring guide rods.

  8. JW says:


  9. JW says:


  10. CAP says:

    So SOCOM just essentially adopted the SIG MCX? I don’t see how this is just an “upper receiver group” when you need to replace the entire stock assembly for it to work. Will these kits not be pemanent conversions?

  11. Thulsa Doom says:

    Ah yes, the old “different pots of money” in action. These aren’t *new* weapons, Senator Congressman, they’re modifications of existing weapons that you already bought. I have no doubt that it would be more cost effective to simply have all new weapons (probably under $200 for complete, assembled lowers) than the manhours needed to convert existing weapons. It’s about Money and MTOE……

  12. Joglee says:

    Looks more like a Mk18 replacement than the SURG initially envisioned…..hmmmm.

    • CAP says:

      Agreed. Whatever weapons these “kits” are installed on, I dont see them ever going back to their original configuration.

  13. Artyman says:

    Uppers aren’t weapons. The serial number is on the lower receiver. If SOCOM wanted to switch “weapons” this is a very painless way to do it. The actual firearms/serial numbered part hasn’t changed.

  14. Walter says:

    So what is this super-duper suppressed upper going to cost per unit? To me this seems to be an incredibly expensive and complicated solution.

  15. JoshZ says:

    What about the URG-1? Who was that for?

    • Cpt M says:

      URG-I was built for USASOC. It’s set up

      • Cpt M says:

        It’s set up pretty much as a standard M4 but with a mid length gas system, new handguard and charging handle. Likely it will be run suppressed full time so USASOC didn’t feel like joining in on SURG.

  16. Patrick Ruster says:

    Are we trusting the MCX recoil spring system yet? I know early units had lots of issues, have these all been ironed out?

  17. Rob says:

    Is that paracord woven into the suppressor guard?

  18. Rob says:

    An American Oversight in military contracting- SIG a German owned company won a US military contract to replace and supply all of our US military handguns. It’s a near $600 Million dollar initial contract that will inclusively grow to 6 Billion dollars over the years. This contract should have gone to a US company for both economic and strategic reasons. Based on the Mil-Spec and review of the competing weapons, at least one of the US Companies had an equal or better submission. The official reason for why SIG was chosen over the better choice is cost, however, the same money will be spent, its only been shifted to different times in the award. It would be naive to pretend that other influences don’t play a part in an award this large, but the public and decision makers should know that SIG SAUER not only pays big money to lobby, they have infiltrated every military base in the US with people either on the base or in offices just outside, in a disingenuous way to influence decisions from within. From what I see its working. This political fabric tear has both an economic and strategic impact that is destructive to our country. Should I remind everyone that the Germans started both World Wars and not as our allies, as our enemy. One can debate that this German company has a US based sister company that employs US citizens, however, the profit goes to Germany and the bulk of the salary pays German banks and citizens. Our laws protected us from importing our defensive tools so SIG circumvented our laws and built sister companies here to get around the intent of the law. This infiltration not only diverts US funds out of the US, the impact to the American companies that spent millions developing a better product has worn them thin and vulnerable with word of bankruptcy and certainly research and design cutbacks. Let me remind you that these companies are the ones that will fight for the US when times are bad. There is an even more important reason this should have never happened. Small arms are arguably a very important tool in our military, and those weapons are now contracted and controlled by a country that we have been at war with twice in the past. Even if an alliance is maintained, the complications of where to align and crossing boarders during times of war are not as strategically sound as keeping our equipment here with US owned companies that have the same US based love of their country. Its US citizens that work together to donate their personal materials to be recycled or bicycle companies that stop to make war time parts for our cause. Do we believe we would get the same dedication from our enemy? Was it a good idea to turn our back on those American companies? The US prides itself on designing and providing the best weapon systems in the world for our troops and our success, this purchase gives us the exact same equipment that many other countries have access to. We could have had better.

    Last week a new announcement that the SURG military contract was canceled and replaced with a watered down inferior version of the original spec, and with no competition was awarded to SIG. The new spec has reduced accuracy, reduced durability, reduced muzzle velocity for penetration, and reduced decibel reduction. It does have a nifty folding stock that wasn’t part of the spec and coincidently has the same SIG name that infiltrated all of our military bases. That’s putting both our handgun and our rifles in the same proverbial German/SIG basket. Very dangerous times! That SIG infiltration should be reviewed quickly before we run out of weapons and weapon companies.

    For clarification Sig Sauer was founded as a Swiss-German company but sold to L&O Holding a German company.

    • SSD says:

      So much you’ve said is absolutely wrong, but ultimately, the reason the SURG spec was changed was that in the first two attempts, no one could meet the requirement. The organization which issued the requirement reconsidered its needs and the state of the art, and made some adjustments. That’s how this works. Otherwise, they’d have nothing, once again.

    • John Martin says:

      Hmm Funny I gues does huge manufacturing Facilities in Exeter and Newington, NH don’t exist. As to Sig Sauer Inc, its a wholly owned subsidiary, yes but also happens to be 6 times larger then its European Sister which employs over 200 workers versus over 1200 American Workers, Sig Sauer exports more to Europe and the rest of the world then its European sister companies. 80% of its current line are American Engineered and made, they even produce my1st (1911) and 2nd (P210) favorite guns of all time, and the entire lineup of Sig products (well except for Blaser Rifles and B. Rizzini Shotguns), but produce the entire line in there own 2 American Factories. Fact is Sig Sauer Inc, is a quility well managed operation, so much so that Ron Cohen, its American CEO and President now oversees both the American and European Operations. . Sadly this kind of Management Skillsets and Drive is Sorely Lacking at Colt, Remington and Smith & Wesson.

  19. Rob says:

    This is not even close to SURG other than saying it’s a gun with a suppressor, no other company competed for whatever sub par spec this represents.
    Not an 11″ barrel.
    Won’t have the necessary muzzle velocity.
    Won’t have the long range accuracy.
    The original spec required 600 yard capability.
    Will likely get bullet stabilization baffle strikes.
    Won’t pass the drop test.
    Won’t pass the dB requirements.
    The original spec used M855A1 with chamber pressures similar to a 300 Win Mag
    Won’t pass the flash requirements.
    The area behind the suppressor on top is accessible and doesn’t pass the temperature spec.
    In addition to dB the suppressor probably doesn’t meet spec- isn’t serviceable.
    With a barrel that short the chamber and muzzle erosion will never retain enough rifling in the middle to hold accuracy anywhere near 10,000 rounds especially full auto.
    Still probably doesn’t pass the underwater test… but it does have a folding stock. Someone sold out!

    • SSD says:

      Your whining is great but unless you have evidence someone actually sold out, you need to wind it in.