H&K Suppressed Civilian Rifles With OSS Cans

Photo &copyright Bryan Jones

The big news from Heckler and Koch this year is unquestionably their suppressed keymod MR556 and MR762 rifles that are going to the civilian market. At media day they had them for us to shoot, and everyone walked away with a big simile on their face after running a few rounds through them.

The MR556/762 rifles are notable for their accuracy and reliability, and the suppressor maker OSS out of Utah has been selected by HK to produce suppressors for them. The neat thing about an OSS suppressor is that you can change out the core of the unit for caliber conversions! That means for one tax stamp you get all kinds of different calibers.

HK 556

Photo ©right Bryan Jones


HK 762a1 SD

Photo ©right Bryan Jones


HK 762SD

Photo ©right Bryan Jones


Now for a look at how the cans attach and a peek into OSS’s baffle design:


Photo ©right Bryan Jones



Photo ©right Bryan Jones



Photo ©right Bryan Jones



Photo ©right Bryan Jones


Photo ©right Bryan Jones



Photo ©right Bryan Jones


The official designations for the rifles are MR556A1 SD and MR762A1 SD. The suppressors pair with the rifles very well and together with the rifle they make a fine weapon system.

Alex C.

Alex is a Senior Writer for The Firearm Blog and Director of TFBTV.


  • GearHead

    Damn my Canadianness, I sure wish suppressors weren’t to evil for Canada.

    • Write your congressmen, or MPs, or whatever they call the people in Canada who take your tax money!

      • JumpIf NotZero

        Might as well cut the letters out from a magazine, would have the same effectiveness :

        • José Pulido

          Send them sugar cubes in envelopes, along with your request on an included note.

  • Jon

    So I will assume this rifle will be what ?? $5,000??

    • Probably. The MR752 is what, $3200? Factor in a $1500 can and the mandatory $300 Heckler and Koch tax and I think you are right on the money.

  • An Interested Person

    Alex, did you get to fire the system? How quiet? Any personal opinions?

  • JumpIf NotZero

    That’s an amazingly complex and expensive to mfg looking silencer. Couple that with the extra weight, the cost, and add in HK’s backwards keymods…. PASS.

    • NikonMikon

      The keymod slot oriented in the fashion that HK has it actually negates the need for a second keymod recoil lug because the direction of travel in relation to the component attached is rearward.

      Wikipedia.org: “The KeyMod specifications call out a “recoil lug” on the accessories which is intended to interface with the larger through hole portion and resist slippage of accessories during counter-recoil. The combination of the angled interface of the nut to the KeyMod slot and the recoil lug to the through hole make for a very strong attachment point which will not slip under harsh recoil or counter recoil. It also provides for an excellent return-to-zero when removed and re-installed.”

  • gunslinger

    wait, so the “stamp” is good for the “shell” of the supressor? much like how an AR15 lower receiver is the “true” firearm?

    if that’s the case, why hasn’t anyone else come in with “interchangeable” cores do do a .223/7.62/9/45…?

    • Dan

      everyone is still waiting for proof that this has been approved by the ATF. so far no letter of approval has been provided by OSS – despite repeated requests.

      if it really was approved, everyone would be doing it. hence the extreme skepticism of their claims.

      • gunslinger

        I was surprised bevause no one else was doing this. Makes sense why now

    • Guest

      They have. I don’t recall any companies at the moment(I think Kestrel might have done it, or at least promised to do it,) but it just depends on what part of the suppressor is serial numbered, and whether or not everything’s welded together.

      People don’t do it, because it’s usually too problematic. The easiest way would be for a company like AAC for example, to standardize a certain mount(probably 90t,) then sell the suppressor threaded, not welded, and then sell the parts to the owners.

      Everyone’s too busy competing to make their proprietary mounts popular to try to come up with a cheap solution to different calibers(everyone just uses 7.62 cans on 5.56/5.45 anyway.) For ultimate value, you can already buy 300winmag or 338lapua cans for use on smaller rifle rounds.

      • Dan

        Nobody does it, because it isn’t legal.

        It doesn’t matter what part is “serialized”. What matters is what part it _is_, e.g. what the ATF considers a ‘silencer part’. Just about everything except a direct thread mount is a ‘silencer part’. The outer tube, the baffles, endcaps, recoil boosters, etc are ‘silencer parts’ — serial numbered or not.

        • amfs

          You can see how they skated around this from the pictures above or by seeing them in person. Plus, the cans are in dealer hands already so the ATF has approved the Form 3’s which is in of itself, a letter.

          The internals just direct the gasses into the outter core (which is what actually acts as the suppressor). The internals are just fins.

    • José Pulido

      I think it’s a hairy ambiguity right now, rather than outright illegal.

      You can still buy a .300winmag can and use it on 300wm/308w/6.8spc/7.62×35/5.56nato/5.45×39/300blk, as long as you can find adapters so you can use similar mounts. Or if you’re into extreme long range and real frugal, buy a .338lm can, and use it on all of those lesser calibers.

  • Clone

    I thought that you couldn’t have spare suppressor innards lying about. If true, then what is the point of having different caliber innards? You’d still need a stamp for each caliber.

    • Dan

      you can’t. that’s why everyone is skeptical about OSS’s claims that this is approved. until we see the ATF letter, we will remain skeptical.

      and if the ATF really approved it, the entire industry would be changed overnight and everyone would do it.

  • Lance

    @Gearhead Im American and I don’t like getting a silencer now all you do is tell Uncle Sam you got a “evil” assault weapon by having one.

  • eric

    how quiet is the can

  • Guest

    Looks heavy as hell, and I don’t understand why their engineers were drinking when they designed those keyholes backwards, but I guess it’s probably not THAT big of a deal.

    • I this looks heavy, never shoot a psg1 or msg90, haha.

  • José Pulido

    H&K hipster Germans with their backwards keymod and piston AR-15s. Yuck.

  • steven ling

    And all this time I thought HK “hated” us civilians!

  • Don’t Drone Me Bro

    Backwards keymod… maybe the Germans are trolling us?

    • hkryan

      H&K’s isn’t backwards, everyone else’s is! 😉

    • MichaelZWilliamson

      That’s so you can hang it on a hook.

  • claymore

    Those “swirls” look like they are trying the old “Sionics” swirling gasses idea that didn’t work very well for “Sionics” back in their hay day.

  • Video of the MR556A1-SD in action at SHOT Show. http://www.youtube.com/watch?v=pGbLAlGTWYI

  • Cymond

    I’m also skeptical about the legality of having spare cores laying around. The ATF argues that a single endcap or baffle IS a suppressor. Many years ago, some people started selling “kits” of baffles & end plates without a tube. ATF shut that down very quickly by declaring individual suppressor parts to be suppressors.

    It got so bad that about 6 years ago, ATF was inspecting YHM when an agent saw a box of Quick Detach suppressor mounts. The agent said that the QD system was only used for mounting suppressors, and therefore the QD mounts were suppressor parts, and not legal to sell individually. Fortunately, this only applies to the YHM Wraith pistol-caliber series that was in production at the time. YHM now makes sure to offer other accessories such as a muzzle compensator that also connects to the QD mount, so that the mount is not “only for suppressors”. Likewise, you’ll note that most other QD mounts on the market are also a flash hider, or also a muzzle brake, etc.

  • John Double

    Somebody should slip something into the Amnesty bill that legalizes off the self suppressors,in states that let you hunt with them.