New From SIG SAUER: Suppressed 300 Blk Upper

SIG SAUER’s adding a suppressed upper to their lineup: the SUR300. The new upper — chambered in the ever-so-chic 300 blackout — fits the SIG MCX and a standard AR15 lower. The supper [sic] has some cool features:

– 6.75” Cold Hammer Forged Barrel
– Permanently Attached 19 Baffle Titanium Suppressor
– Free Float M-lok Handguard
– Short Stroke Gs Piston<
– Tunable Gas Block
– Cycles Sub and Super Sonic Ammo

SIG is also including their Matchlite Duo two-stage trigger.

And an adapter that allows you remove the buffer tube from your AR15 and attach a SIG MCX stock. A welcome feature? Bien SUR! No word on official pricing.


  1. avatar Jack says:

    Will the AR adapter accept an AR buffer tube adapter? Second question… If so, will attaching a buffer tube to the adapter on the adapter create a singularity that leads only to the ATF office?

    1. avatar Chris Heuss says:

      1. Yes, maybe
      2. TBD

  2. avatar Chris Heuss says:

    1. Yes
    2. TBD

  3. avatar Hank says:

    I plan on getting an integrally suppressed .300 BLK upper soon. I’ll wait to see what the price is on this. I’ve been looking at that one that’s advertised here on TTAG as well. It’s cool that stuff like this is commonly available now, but there’s even competition in the market. It really wasn’t long ago that all this stuff wasn’t available.

    1. avatar Jeremy S. says:

      SOCOM’s SURG contract (suppressed upper receiver group) is the cause of all of these integral AR uppers we’ve seen in the last year. The GEMTECH Integra was pretty awesome in 5.56 (it’s reviewed on TTAG) and I hear it’s crazy quiet in 300 BLK. LaRue has an interesting looking one. This SIG one shows promise. The Thunder Beast Arms one I shot a few weeks ago was sweet. There are others, too, of course, and there will be more new ones releasing this year.

      1. avatar TX_Lawyer says:

        Thanks for the reviews on these things. I’m probably going to get one if silencers ever get out of the NFA. If they don’t when I get around to getting a silencer, I’m probably just going to sbr the lower or put a brace on it.

        At the rate I’m buying “not silencers” gun stuff, it might be a couple of years before I can afford any kind of decent silencer.

  4. avatar anonymoose says:

    I’m glad they’re finally getting ready to offer the MCX buffer tube plug.

    1. avatar Joe R. says:

      It’s no good without the MCX upper /bolt/ spring system?

  5. avatar TrueBornSonofLiberty says:

    Two things….no word on OAL. If it’s less than 16”, it’s a 2 stamp piece unless put on a pistol lower piece. And finally and most important, integrally suppressed means a ported and tuned barrel. No indication here that’s what this is. It might just be a suppressor welded on to a barrel. In which case, it’s an inferior offering. I’ve been cajoling barrel manufacturers to offer stand alone, properly integrally suppressed barrels with an OAL of 16” for over a year now. No luck yet. Faxon should do it.

    1. avatar BlazinTheAmazin says:

      Not to be a contrarian but an integral suppressor does not necessarily mean that the barrel is ported, only that the suppressor is integral to the operation of the firearm. Yes many designs like the MP5SD do have ported barrels but a ported barrel does not always reduce sound signature.

      My buddy is part owner of a company called D3 that makes an updated AR15 version of the MP5SD (check out their videos on YouTube). For 9mm it makes sense to port the barrel since removing a small amount of gases will lower velocities to subsonic. I guarantee you that if you look at an integral 5.56 there would be no ports as that round is traveling way too fast to bring it down to subsonic velocities and it would actually make the suppressor louder.

      I had asked my buddy about doing a custom build with a 300blk integral suppressor and asked him about porting the barrel. In all his testing, a ported 300blk barrel always made the integral suppressor louder, but ported barrels do work well for things just above the sound barrier like 9mm/22lr etc.

      1. avatar George from Alaska says:

        Well put…. good and accurate info!

      2. avatar John says:

        Just ordered a D3 9sd myself! Cant wait!

  6. avatar TX_Lawyer says:

    “The supper [sic] has some cool features.” I don’t understand. If you wrote that, correct it. If an editor caught it and inserted the sic, change it.

    Sic refers to a mistake/unusual usage that was in the originally quoted material that is not a mistake/unusual usage of the person quoting it.

  7. avatar John says:

    Any news on this? I haven’t seen any details…

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