Subsonic .375 Socom … Silent but Deadly

Tromix round 2

Jeff over at BigShooterist built a suppressed SBR and chambered it in .375 Socom. .375 Socom is the brainchild of Tony at Tromix. You may know Tony’s work on the Siamese AR-15.

Tromix siamese

Well the .375 Socom is a large caliber akin to the .450 and .50 caliber big bores where the casing is so large that a traditional 30rd AR mag becomes single stack.

Tromix round

Here is Jeff’s intro on the .375 Tromix.

 

Here is his second video where he talks a bit more in detail about the round.

 

It is interesting to hear that the .375 Socom sub sonic is 275 gr at 1000 fps. Not too far off from a .45acp at 230gr out of a 16″bbl going at 955 fps. However I am sure the .375 Socom has a better ballistic coefficient than .45 acp.

It sounds rather quiet with the Bowers pistol can.



Nicholas C

Co-Founder of KRISSTALK forums, an owner’s support group and all things KRISS Vector related. Nick found his passion through competitive shooting while living in NY. He participates in USPSA and 3Gun. He loves all things that shoots and flashlights. Really really bright flashlights.

Any questions please email him at nicholas.c@staff.thefirearmblog.com


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  • iksnilol

    I doubt you can get a much heavier bullet than that in .375 caliber.

    Honestly, I’d just go for .50 Alaskan.

    • Gary Kirk

      You can go up to 350gr readily available, but those can be some loonnng bullets for that little case…

    • Anonymoose

      I need a Noreen Bad News in .510 Whisper.

    • Amplified Heat

      50AK is awesome. Plus you can store spent cartridges on your fingertips. More than a bit of a step up, though, considering 500gr at nearly twice that velocity is attainable. Basically a 50/90

      • iksnilol

        Eh, go all the way or don’t bother.

        I am interested in the cartridge for subsonic loads in a Ruger No. 1 or something. From what I understand you can get 2000 joules at 100 meters with subsonic velocity which is the legal requirement for moose here in Norway.

        • Benjamin Goldstein

          I used to run a to Alaskan with a BMG throat on a Ruger Number 3, 1-9 twist 13 inch barrel. Cast Bullet Engineering (Australia) 975 grain Gas check projectile @ 1070 fps was an excellent pig stopper. Ive been working with a Brass manufacturer on making a .510 case dedicated for subsonic work… On a plus side, it runs in a short action with a Woodleigh 535 grain And still stuff 60 grains 2209 in it.. But it’s main purpose is a 850 grain VLD.

  • Gary Kirk

    Wonder how it’d do with Barnes 300gr triple shocks?

    • Anonymoose

      I’d bet Doubletap will load some up once someone big (like RRA) starts making rifles.

      • Gary Kirk

        Ya mean they wouldn’t possibly do it if I make a basement frankenrifle just for me? Hey, I can dream…

        • Anonymoose

          It’s possible they might start up if lots of people make basement frankenrifles. I mean, they do sell .358 Win, .35 Whelen, and .358 Norma, Buffalo Bore sells .50 Alaskan, and Grizzly (I think?) makes .50-110, and no big company has made rifles in any of those cartridges in many years.

    • gordon

      Acccording to QuickLoad, even with a 24″ barrel you could only barely get them to the 1800fps expansion velocity and that is just at the muzzle.

  • Goosey

    The Russian 9x39mm is also “not too far off from a .45acp at 230gr out of a 16″bbl going at 955 fps”… just saying.

    • Anonymoose

      You could get heavier boolits and supers with better BC for .375 than 9×39 (which is always 247-267gr).

      • Gary Kirk

        You mean like these?

        Cutting edge bullets, laser 350Gr. low drag hollow point bt..

        • Gary Kirk

          Maybe Nathaniel F. could do one on that.. The 9.52+/- x 50mm?? Might still have to keep the case a bit shorter for OAL? But hey, I’m just trying to figure this out..

        • Amplified Heat

          How much longer is that bullet than the SOCOM case, though, lol

          • Gary Kirk

            That’s why I said I’d like to move to the LFAR platform.. As far as your question, the bullet itself is 2.078 inches.. By no means near usable in this case.. They were designed for the 450/375 Cheytac..

          • Gary Kirk

            But if you were to go with the 300Gr Barnes that I was talking about, the length is around 1.493. Which is doable in a .308 action.. And could give you your subsonic, while 270gr loaded a bit warmer could provide the supersonic.. Just my .02

          • gordon

            I would like a higher pressure .375 LFAR round very much too. I haven’t tried to figure one out myself but assume that there are good reasons we haven’t seen one yet. I expect that excessive bolt thrust is the biggest one. I imagine that some of the very knowledgeable guys on the .375 SOCOM forum would share what they know about it if you asked. Probably Tony himself would chime in.

          • gordon

            It is 2.078 the SOCOM case is 1.575 with an OAL of 2.26.

        • gordon

          Very little space left in the case and with a 35,000psi limit you couldn’t even get them to their 1,400fps expansion velocity from a 24″ barrel.

        • Giolli Joker

          Beautiful bullet.
          I guess it fits better a .375-408 CheyTac, though.

    • 9×39 is an 259gr hardened steel AP subsonic that can defeat 8mm of steel plate at 100m, and 30 layers of Kevlar at 200m.

      It’s far and away more badass than either .45 ACP or .300 BLK.

    • iksnilol

      As far as I know, no 16 inch barrels have been made for 9×39.

  • DrewN

    As a very early Beowulf adopter it pains me to say that .458 Socom clearly rules this category.

    • gordon

      I am reposting this since it seems to have been moderated out due to a link the 458SOCOM forum. I apologize if it is double posted or was nixed for other reasons.

      I agree. I have been watching the .375 Socom development since Tony
      first started asking about interest. I really like the concept. However,
      it suffers from a lack of available appropriate bullets. If you read
      the .375 SOCOM forum on the 458SOCOMFORUMS you see that they have pretty much round that the 200gr Sierra Pro Hunter is the best available supersonic bullet, as the 235 Speer HC is inaccurate out of the guns for some
      reason. I have not been able to find 375 bullets that expand at subsonic
      speeds. Lehigh and Outlaw State bullets make quite a few for the .458 and most
      of them have adequate BC for likely subsonic ranges. The 500gr hollow
      point probably has about a .290 BC and that is enough for it to still be
      moving at about 917fps at 150yds – that is 934fp of energy – more than
      these .375 275gr (I didn’t know that Sierra made a .375 275gr)
      at the muzzle. And the .458 is already much bigger even before
      expansion. I, myself, have a .338 Spectre I find the 300gr Nosler Custom
      Comps rarely (never) make a sonic crack when I load them to 1050fps. Nosler
      also claims they have a .8 BC which is fantastic if true. What is kinda
      nice about these and the Matchkings is that the air pocket in front
      makes them tail have and they tumble. My Noslers tumble once at 12″ in
      gel and then exit at the end of the 20″ of the block never to be seen
      again. 290 OS EXOTS look to be even better since they expand and
      fragment rather than just tumble once. The also have a (claimed) .6 BC which is better than any .375 SOCOM bullet’s BC. Anyway, I posit the .458 SOCOM,
      the .338 Spectre and the .300blk are all better subsonic cartridges
      mostly due to appropriate bullet availability.

      • Giolli Joker

        I love the concept of the .338 Spectre… too bad it has not seen the same success of the 458 SOCOM.

        • gordon

          I think it is the lack of an expanding bullet in the 170-200gr range and the fact that it uses 6.8 bolts and magazines. I have some Hawk 200gr round tips with .025 jackets and exposed noses on the way and will post the gel test results on the .338 Spectre forum in a couple weeks or so. Others have used Hawk bullets and reported jacket separation problems, albeit not with the 200 RTs (I think). I have found that I can only push 200gr Speers to about 1650 with my 10.5″ barrel so the bullets have to be specially made for low speed function. I posted a picture of my Speer 200gr HC and 300 Nosler gel test on the .375 forum. You can see the the Speers went through like ice picks. I am perplexed that some .338 Spectre people seem to be using non-expanding bullets like these hunting – I am not a hunter myself though, so perhaps I just don’t know that/how you can use use such an ice pick to ethically take an animal.

          • Giolli Joker

            Thanks for the info.
            Can you please post (broken) links to the forum discussion you mention? I’m curious. Thanks.

          • gordon

            The Hawk problems discussion? It was titled
            “Hawk Bullet discussion.” and was started by
            “JustaPhule” /index.php?topic=1139.0

            I have have not tried or seen others results for the the 240CF. I just don’t have that much confidence in those petals penetrating far enough to make up for the small size of slug that does penetrate deep. I sent them an email asking if it was safe to push them past 1200fps but they didn’t answer. I do like and buy other Lehigh bullets a lot though.

  • Jeremy

    If you are doing subsonic only this seems like not much better than a 220 out of a 300 Blk, except that you only get 10 rounds. Conversely I can send a 600gr pill subsonic out of my 458 socom. I think 375 socom shines more with supers out to 300 and beyond.

    • gordon

      I agree. I have been watching the .375 Socom development since Tony first started asking about interest. I really like the concept. However, it suffers from a lack of available appropriate bullets. If you read the .375 SOCOM forum on the 458SOCOMFORUMS .com you see that they have pretty much found that the 200gr Sierra Pro Hunter is the best available supersonic bullet, as the 235 Speer HC is inaccurate out of the guns for some reason. I have not been able to find 375 bullets that expand at subsonic speeds. The Outlaw State bullets make quite a few for the .458 and most of them have adequate BC for likely subsonic ranges. The 500gr hollow point probably has about a .290 BC and that is enough for it to still be moving at about 917fps at 150yds – that is 934fp of energy – more than this fellows 275 (I didn’t know that Sierra made a .375 275 Matchking or GameKing) at the muzzle. And the .458 is much bigger even before expansion. I, myself, have a .338 Spectre I find the 300gr Nosler Custom Comps rarely make a sonic crack when I load them to 1050fps. Nosler also claims they have a .8 BC which is fantastic if true. What is kinda nice about these and the Matchkings is that the air pocket in front makes them tail heavy and they tumble. My Noslers tumble once at 12″ in gel and then exit at the end of the 20″ of the block never to be seen again. Once again retaining more energy at 150yds than this fellows subsonics at the muzzle. You can also get suppressors that are specifically made for .338 and .458 but not for the .375. Right now I have have several 290gr Outlaw State EXOT bullets loaded up to try for accuracy and in gel. It is said these have a .6 BC. From the images of the gel tests of the .308 EXOTs it should expand enough to do a lot of damage. Anyway, I posit that both the .458 SOCOM and the .338 Spectre are better subsonic cartridges. Probably the .300BLK too, because of the excellent selection of bullets available.

  • Gary Kirk

    Idk, I’m kinda digging this idea.. Would probably move it up to a LFAR platform, and see where I can go from there.. But, I am a sucker for the .375 (love my 700 BDL SS in .375 H&H). And the Barnes triple shocks have a great rep for expansion and weight retention. With the longer case could move up to the 350gr readily

    • LG

      You need to ry the 375 H&H Magnum Ackley Improved. It gives the added case capacity to push the monometal slugs at really god velocities. I have always liked the 375 H&H but the Ackley improved puts it where it was meant to be.

      • Gary Kirk

        Yeah, I wanna do an Ackley improved.. I have an unexplained love for the .375.. In all variants, can’t afford a Chey-tac. And am limited in budget now, also have a LFAR lower half sitting in the safe right now. Trying to think of something different, just cause..

  • Joseph Goins

    What problem does this round solve? None. We have too many calibers on the market today.

    • Badwolf

      Good thing then that problem solving isn’t a requirement, could be just for fun. Free market sorts itself out. If no one wants it it will fade away by itself.

      • Gary Kirk

        I want it.. Well, a slightly different version of it anyway..

      • Joseph Goins

        And it will fail like many many other tactical items (mainly AR accessories) due to over saturation of the market.

        • Badwolf

          Yes, if no one buys, it fails. If a new player wants to enter a crowded market that’s his risk. For the consumer more choice is good, not bad. As I said, free market sorts itself out.

      • DIR911911 .

        the “free market” favors cheats and criminals

        • Badwolf

          caveat emptor, caveat venditor.

    • Gary Kirk

      No such thing, use what you want, the rest of us will continue to explore new territory.. Have fun with your muzzleloader, cause God knows there was only one caliber of those.. Experimenting leads to progress brother.. Enjoy the sport in your way, we will in ours. And who knows, maybe we’ll find out that one caliber you’ve always wanted… TBD

      • Joseph Goins

        Clearly you don’t know muzzleloaders.

        • Sunshine_Shooter

          It was sarcasm.

    • Sunshine_Shooter

      Your claim has been made by countless others just like you for over a century, yet here we are with “too many calibers” and everyone is better off for it.

      • Joseph Goins

        Rule of thumb for me: if the Ruger 10/22, Remington 700, Glocks, or Smith and Wesson revolvers haven’t been chambered for it, we don’t need it. We only really need: .22LR, .223 Rem, 5.45 Soviet, .243 Win, 6.5 Creedmoor, .300BLK, .308 Win, 7.62 Soviet, 7.62v54R, .357Mag, 9mm, .40S&W, .45ACP. Everything else is either novelty (ex. 6.8 SPC, 6.5 Grendel), company specific (ex. 5.7x28mm), or a range toy (ex. .338 Lapua, .50BMG) for civilians.

        And there is nothing wrong with that. Range toys are fun to shoot. Novelty rounds have their place. Company specific cartridges get annoying though. (I say that as a proud owner of a .408 Cheytac.)

        • iksnilol

          But no Ruger 10/22, R700, Glock or S&W has been made in the soviet calibers. Whilst the Remington 700 has been chambered for .338 lapua.

          • Joseph Goins

            This here is ‘Merica. We don’t need no Commie calibers.

        • Sunshine_Shooter

          Why do we need 5.45×39 if we have .223 Remington? Do we really need 7.62×39 when we have .300BLK? What can the Soviet rounds do that the American cannot? Or vice-versa? Do we really need .308 when we have 7.62x54r? Why have 9mm, .40, AND .45 when the .40 is just trying to be the other two combined?

          Why did you not include the .22 mag or the .17 HMR? Cheap rimfire rounds that pack a wallop far above the .22lr, yet still smaller and more manageable than full on .223. And why no bear-worthy revolver calibers? Is .44 magnum not worthy, even though it’s been chambered in a S&W revolver? Does it need to be bigger? Would a .454 Casull be enough? Limiting everybody to .357mag seems a bit harsh, especially when people want to carry light revolvers. I’d put in .38spl or .327mag.

          The point of specialization is that for every possible scenario a perfect solution can be made. Most people will never encounter more than one of these niches and the sheer amount of calibers out there may look ridiculous, but once you realize that everything exists for a reason, the statement “THERE ARE TOO MANY OPTIONS!” becomes quite ridiculous. As an owner of a CheyTac of all things, you should understand this!

          P.S. Really? A Cheytac? Jeeeeeeze. 🙂

  • mazkact

    Am I the only one who is amused by the fact that we are now trying to replicate Nineteenth century single shot rifle ballistics in our MSRS ? As a fan of Sniders,Trapdoors and Rolling Block rifles I follow these “improvements” with glee.I also like the looks I get when I tell someone that my Nineteenth century Swedish Mauser shoots a 6.5 🙂 I truly am not casting any dispersion as I am for anything that advances our hobby/sport/lifestyle. I am currently in a state of regression, black powder cartridge rifles to be precise and am quite certain that eventually this regression will lead me to chunking rocks;)

    • Sunshine_Shooter

      If those single shot rifles from the nineteenth century had suppressors on them, we would currently be exploring the wonders of small caliber, high velocity cartridges 🙂

  • Christian Hedegaard-Schou

    The .375 Socom is a necked down .458 Socom.

    I don’t understand why you would make it subsonic when you can load up 400, 500 and 600 gr bullets in the 458 Socom at subsonic speeds.

    I guess you would get a bit of a ballistic advantage with lower BC bullets, but how much does that really count for at 1000fps?

    That said, the 375 Socom is an AWESOME supersonic thumper for a small platform like the AR15.

    • DIR911911 .

      that’s where I was thinking it would shine , otherwise there’s no real advantage over the subsonic 458.

    • gordon

      I ran the numbers with a maximum point blank range calculator and with the only expanding subsonic round that I know of for the .375 (the Maker 325gr RNHP) which I guesstimate may have a BC as high as .33 and the Outlaw State 500gr RNHP which I guesstimate has a BC of perhaps .29. At 1000fps there is less than a 1 yard difference in the MPBR. Both are about 90yds. I used a 4″ target/vital zone for the calculations.

  • Bert

    If you want me to buy a ridiculous mega cartridge, the bullet should be fist shaped and have a depleted uranium core. Everything else falls short on the gee-whiz meter.