Why are firearm cartridges limited to 63000 psi?

I noticed that even the most powerful big game/anti-materiel/extreme long range cartridges peak at approximately 63000 psi or 425 MPa. I'm guessing that going higher would cause case ruptures, as the tensile strength of brass is about 500 MPa. However, cartridges come in steel case too, and tanks use steel cases exclusively. These exceed 500 MPa, with Korea's latest K279 ammo having a pressure of 700 MPa and a velocity of 1800ms/5900fps. Modern maranging steels have a tensile strength of 2GPa. Why can't we develop hypersonic ammo for infantry with these materials?

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  1. 4 weeks ago
    Anonymous

    My dude, where have you been? The m7 in .277 has been developed and adopted already

    • 4 weeks ago
      Anonymous

      Need a ruger number one in 277 fury to really play with frick you pressures

      • 4 weeks ago
        Anonymous

        in a no. 1 you can do that in any caliber, the case is fully supported.

      • 4 weeks ago
        Anonymous

        I should go with this idea for my sci fi setting which already has 19th-century-empires-in-space vibe. Armor technology gets so strong that armies start looking into older falling block/rolling block designs to build rifles strong enough to shoot DU darts at frickoff mach 6+ velocities.

    • 4 weeks ago
      Anonymous

      Need a ruger number one in 277 fury to really play with frick you pressures

      Yeah sure your 7-08rem upped to ALMOST 270win ( not even 7x64 brenneke) scam is here to stay sure
      >Bbbbut muh 11k rayfeul kontrakt !
      11k rifles is nothing and the contract was there to push for the adoption of a computarized optic, wich would stay but the gun won't.

      • 4 weeks ago
        Anonymous

        You have no idea what you're talking about.

        • 4 weeks ago
          Anonymous

          >One liner comeback deflection
          >No argument besides that

          Develop or stfu

          • 4 weeks ago
            Anonymous

            >The truth
            >Uhm, actually that's the xyz fallacy, so you're wrong

          • 4 weeks ago
            Anonymous

            You're the one arguing supposition, though.

      • 4 weeks ago
        Anonymous

        I like a lot of calibers lmao, I’ve got almost a dozen encore and contender barrels not to mention no 1’s and h&r single shots, and most of them are more obscure than 277 fury
        I get that youre not an enthusiast

      • 4 weeks ago
        Anonymous

        Why you hating? I love frick you pressures regardless of cartridge

        • 4 weeks ago
          Anonymous

          except it will never see use with the frick you pressures. on paper, it will. in practice, they'll use the lower pressure training ammo almost exclusively for the same reasons that people put carry handles on the side of their handguards.

      • 4 weeks ago
        Anonymous

        >11k rifles is nothing and the contract
        You know it's a 10 year contract with a deadline every year to place the next year's order...right? The FY24 order was for 17000 rifles. The FY25 order will likely be around 25-30k. We should see a draft procurement budget by march or april for FY25.

      • 4 weeks ago
        Anonymous

        >Bbbbut muh 11k rayfeul kontrakt !
        the moment someone starts babbling like this is when I safely disregard their opinion. this strategy has never, ever led me astray, and it has saved me from completely reading many posts written by third worlders

    • 4 weeks ago
      Anonymous

      >then
      Learn to write

    • 4 weeks ago
      Anonymous

      Yeah, we increased pressures and found that it improves performance a tiny bit while making everything else worse. Reliability, cost, weight, accuracy, heat, the list goes on. All to...increase range? Nope because other rounds can do that better. Penetrate armour? Nope, doesn't defeat lvl IV. Just another reason the NGSW program is the biggest US small arms fail since the M14.

      • 3 weeks ago
        Anonymous

        >biggest US small arms fail since the M14
        >history rhymes
        Does this mean the next rifle will achieve M16 godhood?

        • 3 weeks ago
          Anonymous

          >the next rifle will achieve M16 godhood?
          Yes. Because the next rifle will be an upgraded M4 using the hybrid case technology, a stellite barrel liner, and a stronger steel for the barrel. Maybe with the KAC bolt and gas system as well

  2. 4 weeks ago
    Anonymous

    Because then the gun would have a shit fricking ton of recoil, be massive and be deafening. Are you asking why infantry doesn’t just carry around a fricking cannon?

    • 4 weeks ago
      Anonymous

      Not to mention 1/10th the barrel life. Consumers aren't going to tolerate barrel changes, where now nobody outside competition shooting schedules will ever reach the end of barrel life of a traditional cartridge like .223 or .308. Start putting hypervelocity shit out and people will have to swap barrels every few years and that won't be tolerated.

      • 4 weeks ago
        Anonymous

        Cost not withstanding, is there no alloy that would allow for hotter pressures and comperable barrel life?

        • 4 weeks ago
          Anonymous

          Well to support higher pressures you need higher "toughness". Toughness is a function between hardness and malleability. Here's a little example.

          The only way to extend barrel life is to make the barrel much harder than the projectile. The harder the barrel, the less wear the projectile can impart on it. That's why barrels get lined with very hard, durable materials after being milled.

          The drawback is that the harder you make the barrel, the more brittle it is, and it can't take the kind of pressures you want to put it through. SOME wear is inevitable, and we're rapidly approaching the point where diminishing gains make it impractical to further pursue anti-wear materials, at least for small arms.

          For joe schmoe a crome-lined barrel is gonna work just fine.

        • 3 weeks ago
          Anonymous

          Barrel steel is only hardened to about RHC 28-32. That's about 1GPA tensile strength. Maranging steel could go double, but they limit the hardness to maintain a certain level of toughness for safety. However, the maraging may be able to have similar toughness at a higher strength than economical 4140 steel. Matweb is down right now.

          When it comes to high velocities though, you're limited by the speed of sound of the working medium. If a pressure wave can only move through your hot combustion gas at 5500 fps, no amount of additional force will let you push something 5501 fps. The energy efficiency of the cartridge goes down on a curve as you approach the speed of sound of your working medium. You need hot hydrogen or helium to get over 20,000 fps.

          The M5 in .277 weighs like 14lbs, and a lot of that is thicker barrel profile, especially towards the chamber. Higher pressures will have a weight trade-off, unless you're using some expensive exotic high performance material.

          High pressure is good for boosting ammo capacity though. The way the 30 super carry keeps up with 9mm is by running at 50,000 psi.

          • 3 weeks ago
            Anonymous

            >The M5 in .277 weighs like 14lbs
            Wrong. It weighs like 8.5 lbs. And don't come back with "yeah, but suppressor and optic and loaded mag, etc..." because none of those have to do with barrel or chamber strengthening.

            • 3 weeks ago
              Anonymous

              Huh. The 14lbs figure came from a Forgotten Weapons video a couple years back. Ian specifically pointed out the thick barrel profile and described how front heavy it was. Wikipedia says 9.84 with the suppressor.

          • 3 weeks ago
            Anonymous

            >If a pressure wave can only move through your hot combustion gas at 5500 fps, no amount of additional force will let you push something 5501 fps. T
            The Rh-120 can achieve up to 1750 m/s with really good efficiency (~30%). The propellant itself can be altered to generate more light gases and the way propellant is burned matters, an assisted rocket projectile can go even faster without any special propellant.

      • 3 weeks ago
        Anonymous

        Do you think hybrid cases can be treated the same way hollow points are for pistol ammo? FMJ for practice/range time, JHP’s in your carry mag. Brass case for training, hybrid case for when you’re actually shooting stuff.

    • 4 weeks ago
      Anonymous

      So what? Just design them as recloiless.

    • 4 weeks ago
      Anonymous

      Pressures used to be much lower. Go back to WW2 era and 22kpsi or 40kpsi were common. Back then it was about chamber strength and other factors but today the limit is brass pressure-brazing to a bolt. Stellite barrels fix the wear issue.
      Yes, we could do hypersonic ammo: https://techlinkcenter.org/news/us-army-researchers-are-turning-it-up-to-11-to-make-hypervelocity-firearms/

      PV=nRT
      Pressure has no downside if you can build a gun which takes it. It's a 1:1 for efficiency. You can double the pressure and halve the propellant for the same MV, while reducing the recoil because now you're expelling less mass.

      • 4 weeks ago
        Anonymous

        >a cartridge that contained less than a gram of propellant (15 grains). The muzzle velocity was over 2,900 feet per second
        High pressure gives M4 performance from a MP7 size gun and cartridges.
        It also gives insane beltfed performance:
        >the U.S. Army’s new 24-inch prototype barrel produced muzzle velocities of 4,600 to 5,750 feet per second.

        • 3 weeks ago
          Anonymous

          > High pressure gives M4 performance from a MP7 size gun and cartridges.

          THIS is the point, YES. High pressure makes new categories of guns possible.

      • 3 weeks ago
        Anonymous

        >today the limit is brass pressure-brazing to a bolt
        What about the factory Teflon lubricated 5.7 shit, how does that play into it?

    • 4 weeks ago
      Anonymous

      Yes

    • 3 weeks ago
      Anonymous

      NTA. No it would not. That is determined by the momentum of ejecta and gun mass. You don’t need to crank up the pressures on existing cartridges. You can scale down their case sizes while maintains the same performance. Imagine a 5.7x28 with m855 ballistics.

  3. 4 weeks ago
    Anonymous

    Because case strength isn't the only factor here :
    Rifle system needs to be light enough, higher pressure requires heftier locking systems ( at least in autoloaders)
    - higher chamber pressure also put a bigger strain on the barrel, more precisely in the chamber throat and muzzle end (crown) areas and thus will decrease barrel life (338lm, 6,5-284 and 300wm/rum/prc all have shit barrel life)
    - higher pressure, let's say 80k psi like the 277 scam (7-08 upped to 270win by high pressure), requires new types of powders and thus load data...
    - you need more than just steel cases, you also need a pressure proof case head with dedicated priming system ( the 277 uses washers inserts for priming pockets)

    All of this so you can either reduce your case dimensions to match a bigger cartridge ( see 277 shill furry) or get a few hundred fps more velocity in precision shooting setups....

    Tldr : the juice isn't worth the squeeze for handheld firearms, tanks and autocannons? Sure.

  4. 4 weeks ago
    Anonymous

    1. brass limits max pressure
    2. even without 1., chamber thickness increases exponentially with pressure, going beyond 0.25-0.5 of the UTS isn't a good idea weight-wise.

  5. 4 weeks ago
    Anonymous

    The brass.
    Brass fails much above that, the steel case head on the 277 fury or whatever is supposed to fix that.

    • 4 weeks ago
      Anonymous

      >steel case head
      Wouldn't the sides fail then?

      • 4 weeks ago
        Anonymous

        Sides dont experience such a high peak pressure

        • 4 weeks ago
          Anonymous

          So is the peak pressure achieved right after the primer detonates and ignites the powder charge?

          • 3 weeks ago
            Anonymous

            Peak pressure is usually achieved once the bullet begins engraving. Some faster powders will achieve that before then.

        • 4 weeks ago
          Anonymous

          so can i put the steel ass on any case and have frick you pressures in any gun

        • 4 weeks ago
          Anonymous

          Close but not correct.
          The sides of the case are supported by the chamber. They don't need much strength. The case head, however, is unsupported to a certain degree, so it has to contain the pressure on its own.
          Read Hatcher's Notebook by Julian Hatcher, it covers this well.

      • 3 weeks ago
        Anonymous

        Sides are fully supported by the walls of the chamber.

  6. 4 weeks ago
    Anonymous

    tank barrels are rated for only 300 or so high pressure APFSDS rounds

    • 4 weeks ago
      Anonymous

      >300 or so high pressure APFSDS rounds
      Russian tank barrels with sabots with fins points of contract. NATO guns rated to about 1000 APFSDS.
      BTW battleships guns were rated to just 200-300 rounds (1-2 full magazines) with normal pressures. The larger calibers the faster it erodes the barrel, erosion is due to temperature and larger caliber has longer time of the shot, temperature acts longer.

      • 4 weeks ago
        Anonymous

        M256 has an estimated lifetime of around 1800 EFC, one M829A2/A3 corresponds to 4-6 EFCs, that's around 300-450 rounds. I don't think there is any APFSDS in service that would get you to 1000, not even the oldest cold war stuff since it used more corrosive propellants. Soviet guns are somewhat worse, 800-1200 EFC and 3-5 per round. Most of the erosion happens due to hot gases, scratches from fins or sabot are less significant

  7. 4 weeks ago
    Anonymous

    Siggers stay losing

  8. 4 weeks ago
    Anonymous

    Tensile stress =/= pressure. 425 MPa pressure does not cause 425 MPa stress to case.

  9. 4 weeks ago
    Anonymous

    Nobody uses steel case ammo in modern tank guns anymore. Anything 120mm/125mm uses combustible cases to avoid these issues. The old NATO L7 derived 105s use steel case but those were limited to ~550 MPa

  10. 4 weeks ago
    Anonymous

    Firearm manufacturers are stuck to old fashioned designs.
    Look at the new NGSW, they managed to finally use a steel base but even then they still use a brass case and the pressure increase is pretty pathetic.

  11. 3 weeks ago
    Anonymous

    You're making the same mistake as early shipborne cannons.
    "Big boom doesn't make deader"
    The conclusion was "less powder, smaller cannons, more small projectiles and more small cannons".
    Most of the energy is lost if your bullet flies straight through the target.
    Ask yourself: What problem are you trying to solve with your ammo, and how do you make sure, that within standard engagement range the energy is transferred into your target and not the wall behind him?

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