.277 Wolverine Cartridge is now in the Public Domain

Many of you may have read the title and asked: “What in the world is a .277 Wolverine?”. So first, let’s see what cartridge it is. In a nutshell, it is a wildcat cartridge based on .223 Rem or 5.56 NATO case with a .277 caliber (6.8mm) projectile. It is developed by Mad Dog Weapon Systems.

L-R: .223 Remington, .277 Wolverine, .300 Blackout, 6.8 SPC

The .223 Rem shoulder is moved back and the case length is shortened. The overall length of .277 Wolverine (.277WLV) is 2.26″, which makes it possible to fit into AR-15 magazines. Just like the .300 Blackout, it only requires a barrel change to build an AR-15 rifle chambered in this caliber. In fact, this cartridge comes pretty close to the 6.8 SPC but lacks the disadvantages associated with the latter (need of a different/optimized magazine and different bolt, reduced magazine capacity etc.). Particularly, the .277 Wolverine pushes a 90 gr, 100 gr and 110 gr projectiles at 2700 fps, 2600 fps and 2500 fps respectively (from a 16″ barrel). There you have a brief description of the cartridge. For more information visit MDWS’s website.

As the title of this post implies, the designer of this cartridge has released it to the public (effective of April 18, 2017). It means that this cartridge is no more a proprietary one and anybody willing to manufacture it can do it without a need to have a permission. However, it doesn’t mean that the cartridge is standardized. Being in the public domain shouldn’t be confused with being a SAAMI standard. In the statement released on their Facebook page, MDWS’s CEO Mark Kexel says:

As you can see, the MDWS .277 Wolverine has grown leaps and bounds since it’s original launch just a little over 3 years ago. In fact, it has grown faster than most Wildcat cartridges that became SAAMI registered cartridges. We strongly feel SAAMI registration is just around the corner.

Considering that MDWS has also recently become a SAAMI member, I think chances are good we’ll see a new SAAMI cartridge soon.

MDWS has also released the chamber and gauge dimensions of the .277 Wolverine:

.277 Wolverine chamber dimensions

Dimensions of .277 Wolverine Go, No-Go and Field gauges

I think this is a very wise move by MDWS for a number of reasons. First, if somebody has designed a really successful new wildcat cartridge, but keeps it proprietary, it is a matter of time that a major manufacturer will make slight dimension changes and standardize basically a copy of that cartridge. Second, allowing other manufacturers to freely make the cartridge and products related to it (barrels, reloading dies etc.) will boost the popularity of the design and will be a good promotion of the original company that has introduced it.

Hrachya H

Being a lifelong firearms enthusiast, Hrachya always enjoys studying design, technology and history of guns and ammunition. His knowledge of Russian allows him to translate and make Russian/Soviet/Combloc small arms related information available for the English speaking audience.
Should you need to contact him, feel free to shoot him a message at TFBHrachyaH@gmail.com


  • 22winmag

    So thrilled to be first on this topic!

    .277 is never a bad decision.

    • Jared Vynn

      It’s getting roughly the same velocity as 243 Winchester would in a 16″. Would be a great hunting round.

  • So… it’s basically a slightly shorter 6.8 SPC.
    I’m kinda not impressed. Now, 7mm would have interested me.

    • FightFireJay

      The OAL isn’t the big difference. It’s that 6.8 SPC requires it’s own magazine and bolt because it’s a wider cartridge. The Wolverine is based off of the standard 5.56/.223 brass, so conversion is easier, simpler, cheaper, and… well, you get the idea.

      • HSR47

        This. Given the issues capacity/magazine/bolt/price issues with 6.8 SPC, there’s no way I’m going to mess with it.

        On the other hand, if .277 Wolverine gets wider acceptance, gets SAMMI certification, has better ballistics than 5.56 out of a 11.5″ barrel, I might be willing to mess with it if the price is right. If PA ever gets it’s hunting laws out of the stone age, I might be even more motivated — If the quoted velocities are realistic, it likely beats both 5.56 and .300 blk for hunting.

      • noob

        So can this approach 6.8spc performance because of adding more powder into a smaller case?

    • Phil Elliott

      7mm TCU already exists, mine works very well in a 10″ Thompson contender

  • Evan Ferguson

    Pretty cool. I happen to be a fan of 300blk. It has a pretty limited ballistic range, but I shoot it with that in mind. It delivers good power, in a flat curve out to 200m. Comparing it to the 308, 5.56, etc is just silly. Going from super to subsonic in a magazine change is cool, even if it’s not 22lr quiet out of a silencer.

    As far as .277 goes, sounds excellent! I hope it does well, and a SAAMI spec would really help this thing take off.

    • flashoverride

      Well, 300BLK was originally designed to replace the MP5SD, so you have to take that into account. Have a 16″ build now, waiting on my form 1 for a 10.5″. Shooting with subs is pretty dang quiet.

      • Evan Ferguson

        Yep. I’ve got a 9″ SBR in 300blk, with the BCM barrel. Functions 100% unsuppressed with super and subs and a standard weight 5.3oz A5 buffer. Suppressed works great too. BCM really did their homework with the port size and tuning. Much fun with the echo trigger, altogether very expensive.

        • DanGoodShot

          “altogether very expensive.” Thats why ya gotta reload man. I’m paying pennys a round. Range pickup brass, mil surp/pulled or blem 308 bullets, bulk powder. You’d be amazed how low you can get the cost per round down to.

          • Evan Ferguson

            Yea, I’m aware. I have zero free time, I’m saving it for retirement. I give my empties to my buddy who actually does reload. He appreciates it.

          • DanGoodShot

            Weak. Thats complete bs. I’m a single father of 4 kids who are all under 10 years old. I work 2 jobs and I’m lucky and so, so grateful when I get more than five and a half hours of sleep on a weekend. So, yeah, I call bs. If you just said reloading isn’t for you, I could’ve respected that. Reloading isn’t for everyone. Nothing is.
            Anyway, what my point was, before you go rattling on about things being too expensive. There are ways around the higher prices if your willing to do a little extra work(for me it’s more like a vacation then work!). In this case, the savings are fairly substantial too.
            Sorry if I came off a little harsh on the whole “no time” thing. It’s just that I know too well how precious time is. But when you really want to do something, you make. You don’t use it as an excuse.

          • Evan Ferguson

            Good for you. And yep, still too busy to start reloading.

          • DanGoodShot

            Were ya too busy to reply to my comment? Not too busy.

          • Lo Andy Kruth

            I am also to busy, but having i can answer your rude comments.

          • DanGoodShot

            This why I hate the interweb. My dry sarcastic (all be it maybe bad) sense of humor hardly ever comes through. Once in a blue moon someone gets it. I was just busting balls on the last comment and didn’t mean anything “rude” with ANY of my comments.

          • Ben Pottinger

            Yes, it’s hard to get subtle emotions through quick txt posts. I’m sure many a boyfriend has made a fatal mistake with 140 characters or less. 😉

            One other thing often overlooked that reloading allows is specialty rounds. I make wax bullets for my 45LC revolver sometimes for practice. Use a primer and a plug of wax and you can play “fast draw” without worrying about blowing off your feet or leg!

          • Ben Pottinger

            It also depends on the value of his time. If your working two jobs I suspect your time is less valuable (not to you obviously, but to the marketplace). If he is making 150-200 a year then yes, reloading just to save money would be downright silly. Fun? Yes, accuracy? Yes. Savings? No. Not when your time is worth 70-100$ an hour.

            Now that my time is basically worthless (to the marketplace) reloading is worth it from a savings perspective. Yet before when I was working full time I only reloaded specialty rounds (77gr 556, 175gr 308, etc) for accuracy and savings. I never bothered with 9mm because it was so cheap, same for surplus 556 (which sadly isn’t nearly as cheap anymore).

            I actually sold my 300blk upper (8″ noveske) because while it was really cool it wasn’t any quieter then my 9mm mp5 and was quite a bit more expensive to shoot, even with blem/pulled reloads. If I was a hog hunter or something it would have had value, but just to go “bang” quietly the 9mm is much cheaper.

          • DanGoodShot

            Oh I understand that and I completely agree with you. I was just breakin’ balls. That was just my sh@tty sense of humor. 🙂

          • Sam Damiano

            Tired of the my time is worth X amount an hour. Unless you are paid 24 hours a day you have time that you don’t get paid. If someone elects family time that’s cool but your not getting paid $70-100 an hour after you leave work. That just makes your ego feel better.

          • James Young

            Unless you’re a contractor or in Sales. Then your time is worth as much after work since you can work anytime and make more.

          • DanGoodShot

            Apparently I came off as rude.? Not my intent. I just break balls, It’s my sence of humor… that I should realize by now does not translate well through the interweb. Carry on.

    • Nick

      It’s important to remember that the blackout was never meant for a 16″ barrel. Comparisons between it and other calibers should be based on the same barrel length. Most “analysis” ignores this fact.

      Sure, 5.56 gets 3000+ fps, but only out of a 16″ barrel. Put that same cartridge in a 10″ and there’s a significant velocity drop off. Meanwhile, the blackout has burned all its powder before the bullet even gets to the muzzle the same length barrel. I get ~2250 fps out of my 10.5″ with a 110 Varmageddon. That’s only about 300-400 fps slower than my short 5.56 gets with a 55 grain bullet.

      • mig1nc

        Yep. And 5.56 was designed for a 20″ barrel, where it gets peak velocity.

        That said, the .277 appears to work well in short barrels.

        • mig1nc

          You can also swap supers and subs with just a mag change. Just like blackout. It sort of does everything blackout does, but better.

          I hope it takes off.

  • Joel

    So close and yet so far.
    6.5 MPC lets one use 6.5 bullets. There is a wide variety of them and some have very, very impressive ballistics.

    • FightFireJay

      Most 6.5 cartridges that fit in an AR-15 (not an AR-10) are meant to perform on “External Ballistics” (wind drift, mid/long range target use). The Wolverine is meant to compete more “Terminal Ballistics” (hunting and home/self defense) and practicality of the average user (no special magazine or bolt).

      For long range target shooting, 6.5mm bullets definitely have an advantage, but in a cartridge of this size, the same weight 6.8 bullet gets out the barrel with more velocity and has a wider range of bullets designed to perform at these velocities for terminal effect (hunting and self/home defense).

      It’s safe to say that very few folks are actually long range shooting with an AR-15. Those that do, likely use a 6.5 Grendel or another wildcat. This is meant to compete on a different objective.

    • MclarenF1Forever

      It seems 6.5 MPC didn’t go anywhere. I prefer it over other 6.5 cartridges that fit in an AR-15 platform. The 6mm Mongoose from MDWS is interesting as well, maybe open that up to 6.5, get Hornady & a major firearm manufacturer behind it, and profit.

  • TechnoTriticale

    How the interchange hazard on these for people with .223/5.56 firearms?

    I’m gonna guess that people who own 6.8SPC and/or 300BLK aren’t really customers for 277woolie.

    • HSR47

      The interchange hazard is going to be similar to the hazard posed by .300 blk.

      As for your other point, I have a lot into .300 blk, mostly because it’s fun to shoot with a can, and especially on an M16 lower.

      If I ever got into hunting (which would require PA to get it’s equipment regs out of the 1800s), I’d be willing to consider putting an upper together in .277: If the velocities quoted above are realistic (read: if they’re not just marketing BS), then it’s terminal ballistics should be better than .223/5.56mm and .300 blk by a worthwhile margin.

      • MDWS

        No, the 277 Wolverine will not chamber in a 5.56 without a mallet, and yes, the numbers are real.

        • Hi MDWS, great work on the .277! Really a cool cartridge and I hope it takes off on the commercial market.

          If you don’t mind me asking, will the .277 be SAAMI’d at 55kpsi (.223) or 62kspi (5.56)?

          Hoping for 62kpsi – I think they key to this round crushing the competition will be factories loading it to it’s full potential; if the factory ammo ends up being dowloaded to 2400fps with a 110gr then it will look a lot less fantastic.

      • QuadGMoto

        Your comment prompted a bit of research. The Game Commission had sent out surveys to 4,000 hunters. Of the roughly 2,000 that responded, more than 52% strongly opposed using semi-automatics when hunting big game. So that’s what the commission decided to do (apparently last week). Semi-auto in .22 or smaller is permitted for small game and fur-bearers (I wonder if .223 for coyotes fits into that) and manual action (bolt, lever) is still the requirement for anything bigger. 😒

        • noob

          What animals are legal fur-bearers? Does a bearskin rug count?

          • QuadGMoto

            You could try that, but if the game wardens catch you you’ll probably want to change places with that rug! 😵

            They have a list of what are legal furbearing animals that they send out to hunters every year. They are: raccoons, foxes, coyotes, opossums, striped skunks, weasels, bobcats, minks, muskrats, river otters, fishers, and beavers.

        • Quasimofo

          Don’t get me started on that damn “survey” the PGC put out there. The PGC got the result they wanted, and semiauto inclusion ended up pretty much how many anticipated it would. The Pennsyltucky Fudds gotta move in baby steps, nevermind what they could learn from 48 other states. I’m also guessing a lot more Fudds will have to take dirt naps before Sunday hunting is a reality here, too.

        • HSR47

          They sent out a survey, but the data returned was skewed for a number of reasons:

          First, the methodology for selection was flawed, as has been pointed out by Adam Kraut of TGC/Prince Law/FICG (link below): the selected group does not appear to have been selected to correct for age, geography, or other factors likely to impact results — Older hunters, and those that don’t own non-manual rifles overwhelmingly opposed the move to stop blocking the use of semi-auto rifles, while younger hunters, and those that DO own semi-auto rifles tended to support the move by the game commission to bring PA’s hunting regs into the early 20th century. Since the sampling methodology was “random” and does not appear to have accounted for even easy to factor issues (PAGC should have been able to normalize the survey group for age and geographic location — i.e. ensure that the survey is common percentage of each county’s registered hunters, and that each county’s sample group contained Y% the hunters in each age group.).

          Second, the list they used to send surveys to appears to have only included those who have hunted previously. I know numerous people who would like to hunt, but haven’t because they don’t have equipment that they can legally hunt with in PA. The survey methodology was thus flawed in that regard, because it had no way to account for all the people who were strongly considering getting into hunting based on the proposed regulatory change.

          TLDR: There are strong indications that the survey was BS, and that it may have heavily over-sampled older hunters (the fact that roughly 3/4 of the surveys were returned by mail is a strong indicator of this), which could have easily had a significant effect on the result, given the strong opposition of the hunters in older age groups.


    • Nick

      Actually, doesn’t look like it’ll be an issue. The neck looks like it’s past the shoulder on the .223, which means it probably won’t fit.

      The issue with the 300BO is that its mouth comes before the shoulder on a .223, allowing it to chamber, depending on bullet geometry.

      • MDWS

        You are correct, not an issue.

  • Shaun Connery Oliver II

    Now that this is interesting news, I like to ask, from the heart of a curious individual, one question: IS Lawrence Krammer’s 6.8×45 UCC trying to copy the .277 Wolverine or not? If so, what is your opinion on Krammer Defense’s cartridge? My opinion is that they’re close in performance, but the .277 Wolverine has been around for three years. I am absolutely convinced about the .277 Wolverine!

  • gunsandrockets

    For the most common owners/buyers of an AR who are looking for an alternative to 5.56mm, I can see the appeal of this cartridge over something like the Sharps .25 or the .300 BLK.

    And by most common, I mean those owners who don’t reload, don’t SBR, and don’t use subsonic ammo.

  • In addition to Supersonic performance, the .277 Wolverine can also shoot 175-193gr Subsonic loads. So it offers the subsonic ability of 300blk, but with higher supersonic velocity and better BC bullets.

    It’s a very neat cartridge and had it been released 10 years ago, I doubt there would have been a .300blk or 6.8 SPC today.

    • RocketScientist

      How does it perform out of shorter (10″ or so) barrels?

      • From a test on The Chopping Block with an 8.3″ barrel, 110gr’s were clocking 2050fps and 100gr’s were clocking 2250fps.

        I’d check the .277 wolverine forum for more info, but it appears to do as well or better then .300blk from pdw barrels.

  • valorius


    • SPQR9

      Well, for one reason, some states prohibit use of .22/5.56mm on big game, requiring larger bullet diameter.

      • valorius

        If hunting with an AR is your itch, .300 black out already exists for that purpose.

        • Nick

          This actually has more power.

          • ostiariusalpha

            And 7.62×40mm Wilson Tactical has more power than both. Why would you choose this cartridge when it has less versatility than .300 BLK and less power than 7.62 Wilson?

          • john huscio

            300blk is less versatile since it sucks from a “16 barrel which is what most have. Id switch completely to 277 for home/self defense use if it gets widespread.

          • ostiariusalpha

            Most of the people I’ve seen using .300 BLK have “pistols” with 8-10 inch barrels. Of course, you can use whatever you like, I’m sure it will work mostly fine for just about every application. Just not seeing what it does better than other cartridges.

          • This round actually is more versatile then .300 – it can be loaded with 175gr copper expanding subsonics, as well as supersonics from 90-110gr, which have better BC’s.

            .277 Wolverine 110gr VMAX .370 bc @ 2550fps / 1800fps minimum expansion velocity
            –> 350 yards = 1796fps

            .300blk 110gr VMAX .290 BC # 2350fps / 1800 fps minimum expansion
            –>225 yards = 1750 fps

          • ostiariusalpha

            I just don’t see those yardages as particularly significant for either of these cartridges, that’s well beyond their respective ethical hunting distances and I seriously doubt anyone is going to confuse them for precision rounds. The .300 BLK’s expanding copper subsonics have considerably more power and a wider selection, so having a bit more power on the supersonic end doesn’t seem to give the .277 Wolverine a relevant advantage when considered against much more impressive supersonic rounds; a 6.5x40mm can shoot copper solid subsonics, with supersonic performance exceeding the .277 Wolverine. My perspective is that if you are going to give a 5.56 derived cartridge subsonic capabilities, then that’s where your emphasis should be.

          • 6.5×40 is based on the 6.8 SPC case so while very cool as a round, is not really comparable to the .277 wolverine, .300 blk, 6×45, etc, as the primary purpose of these rounds is to use dirt cheap .223/5.56 brass, and be used in standard 5.56 weapons with a simple barrel change.

            .277 Wolverine has 36% more effective range over .300 BLK in supersonic 110gr. And for CQB/HD use, can use lighter weight, shorter penetration projectiles in the 90gr range.

            The .300 can shoot 25gr heavier subsonics, which is a worthless advantage – 175gr @ 1050fps = 424ftlbs, vs 490ftlbs – essentially a .45 ACP vs .45 ACP +p level of power.

            It offers all of the subsonic benefits of .300 BLK but with much better supersonic performance, allowing it to also replace 6.8 SPC as a hunting / combat round. All while using the readily available 5.56 parent case.

          • ostiariusalpha

            No, Mark, I meant nothing about the “Warrior Magnum.” There are a goodly number of 5.56 derived wildcats that have around a 40mm case length (like this shortened 6.5mm TCU https://uploads.disquscdn.com/images/1a752d7301039f25b45d1ac0b96de42478e25d25d378951ec147b30dca70e685.jpg ), all of which have better supersonic performance than .277 Wolverine. Though they have the capacity to use subsonic loads, they are markedly deficient in that category compared to the .277, just as the .277 is inferior to .300 BLK. The .277 has a ~14% energy advantage with a comparable 90gr supersonic load, but the .300 has a 16% advantage with it’s 200gr bullet. Cutting Edge sells 210gr. bullets, by the way, so it’s a 35gr advantage for the Blackout with 514ft/lbs of energy.

          • The closest I could find to a AR compatible 5.56 based 6.5 cartridge was the 6.5 PCC, which doesn’t seem to have nearly the traction / development of the .277, and had similar velocity #’s (100gr @ 2600fps.) If there’s a better one out there I’d be thrilled to know about it.

            As far as subsonic energy in .277 vs .300, thats a pretty worthless gain – these projectiles are velocity dependent to expand, so two rounds impacting at the same low velocity and low energy are likely to be very similar in performance. We’re essentially talking 40 S&W vs .45 ACP weight and energy change here; the target is unlikely to notice 424 vs 514 ft/lbs in a subsonic load.

            But in supersonic, having an expansion range of 350 yards vs 225 yards is a big deal. The .277 is a credible assault rifle round (3-300 meter performance) and is hitting harder, with better sectional density, BC, and flatter trajectory then the .300 at all ranges.

            Really, just look at it through an alternate timeline, where .277 was released before the .300 blk, and was as popular as .300 is today. In that timeline of .277 popularity, would anyone really choose the new .300 blk?

          • valorius

            So does .50 Beowulf. I don’t see the niche or need this new round fills.

      • valorius

        .300 black out? 6.8mm spc? 6.5mm grendel? .50 beowulf?

        • Quasimofo

          It looks like this 277 Wolverine has a better MPBR (~50+ yds longer) than 300 BLK or any of the AR thumpers. More power for hunting than the 300 BLK and it also doesn’t need specialized bolts and mags, and that’s definitely been a boon to the 300 BLK. And it can use the 6.8 SPC-specific hunting bullets. If someone already has a 300 BLK or 6.8 SPC, they might take a pass on this one, but I can see the potential appeal.

        • SPQR9

          The .300 is too short range for many hunting situations (although hog hunting with it is a blast). The 6.8 SPC and 6.8 Grendel require different bolts and magazines.

          I’m considering an upper in this or .25 -45 Sharps.

          • valorius

            .25-45 sharps seems intriguing.

  • Nick

    I see their in the comment section. I’m curious what the pressure limit is on this cartridge. I’m assuming the same as the parent case, or is it something different.

    What piques my interest in this is that the Yeti cartridge they have had me questioning whether theyre pushing the pressure a bit too far. 55,000 psi on a 5.56 NATO sized bolt face is fine. That same pressure on a bolt face opened up for larger cartridges (like their Yeti or the 458 Socom) raises concerns.

    And while PressureTrace is a cool gizmo, I’m not sure a cartridge designer should be relying on it for accurate data when theyre selling the design.

    • I’d assume / hope the pressure is 62kspi like 5.56.

  • Joe Schmo

    This definitely has my attention. I had read about this cartridge about a year ago, and I’m glad to see it gain some traction. I think the timing is great, 6.5 Grendel was proprietary for how many years until recently, and it doesn’t nearly have the interest it did in ~2006-2007.

    Hopefully this round takes off and we see more diversity in a world of bland ARs, haha.

    • int19h

      6.5 Grendel might not have the interest, but it has readily available super cheap Russian ammo…

  • Disagreeable

    This is a great cartridge for the AR. I find it difficult to compare this round with any other because of its stand alone merit. As the article and some of the comments have stated, there are advantages. Extended range over the 300 blk is one, no special mags or bolt needed, and another is plenty of available brass and bullets to process your own ammo or purchase from http://www.jbsfirearms.com. I own a 16″ 300 blk and a 16″ 277 wolvie, shoot mostly supersonic and enjoy them both!

  • Renato H M de Oliveira

    it is a matter of time that a major manufacturer will make slight dimension changes and standardize basically a copy of that cartridge

    300 Whisper says “hi” to 300 Blackout.

  • No one

    So, someone managed to make an even worse version of 6.8mm SPC?

    Quite impressive actually.