Why do IFV's use necked cartridges? It doesn't make sense to me.

Why do IFV's use necked cartridges?

It doesn't make sense to me. An IFV wants to have a large caliber HE shell for infantry etc. and a sub caliber dart for armored targets.

So why isn't everyone just taking the small 25 mm shell that you can carry a frickton of and making it straight walled so you can lob heavy big 40 mm grenades with low velocity and still shoot effective darts?

That would be the best of both worlds, good payload, good ammo capacity, and good penetration, and while you're at it, make the case telescoped and out of plastic.

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  1. 4 weeks ago
    Anonymous

    CT ammo has ongoing issues to resolve regarding cost, heat sensitivity, durability, and sealing. Those problems have to be solved before CT ammo can be taken seriously.

    • 4 weeks ago
      Anonymous

      Why do you lie? Literally all of those problems were already solved long ago in the 90's by Eugene Stoner.
      Besides, this thread isn't mainly about CT.

      • 4 weeks ago
        Anonymous

        Not enough benefit at the current state of things to justify the enormous disruption and cost of changing over. In this specific case it's similar to, I dunno, 9mm even: yeah you can 100% design something with current materials that does somewhat better. But it's not like it's 5x better, so it's not worth the disruption until you're doing something else anyway. Eventually something like it will probably happen through attrition and as they make entirely new platforms (autonomous), and tech like smart rounds may get mixed in. But it takes a lot of justify a redo given enormous existing ammo stockpiles and platforms.

        • 4 weeks ago
          Anonymous

          New IFV calibers are developed all the time, stop with this bullshit legacy argument.

          Besides, the straight walled cartridge case is the single most basic case type, not new technology.

      • 4 weeks ago
        Anonymous

        CT cartridges have potential issues that aren't really convenient to deal with.
        They introduce problems like a cylinder gap and alignment into the action.
        So now you have to have 100% reliability on the casemouth sealing against the forcing cone, otherwise gas jetting will cut up your action.
        And alignment, with the projectile having to strike and be directed by the forcing cone properly for accuracy is potentially hard to achieve with spitzer projectiles, especially ones with long ogives.

        >problems solved in the 90s
        Prove it.
        His ACR gun went nowhere.

        • 4 weeks ago
          Anonymous

          Hard to achieve with Spitzer projectiles, and also probably impossible to achieve with other types like sabot darts and the like.

        • 4 weeks ago
          Anonymous

          >His ACR gun went nowhere
          Nobody adopted the Stoner 96 either despite it being an excellent LMG far superior to the fat shitty pig that is the M249

          • 4 weeks ago
            Anonymous

            On paper, at least.
            But that was a mix of bad timing, and Stoner not entering his gun in the SAW trials.

      • 4 weeks ago
        Anonymous

        >lack of proper heat dispersal requires active cooling, else a low sustained rate of fire
        >square-cube law means that thermal energy is increased by the third factor for a increase of barrel area in contact two times larger
        Albeit, we have very good energetics that aren't hygroscopic, and can take a beating. Heat sensitivity will always be lower given the reduced density and properties of propellant, but again that can be accounted for.
        Cost is definitely harder to work around without compromise.

        • 4 weeks ago
          Anonymous

          What the hell are you talking about? Do you even know what CT is? Are you a chatbot?

    • 4 weeks ago
      Anonymous

      >CT ammo has ongoing issues to resolve regarding cost, heat sensitivity, durability, and sealing. Those problems have to be solved before CT ammo can be taken seriously.
      You're thinking of caseless ammo. CT doesn't have any of those issues.

  2. 4 weeks ago
    Anonymous

    Someone didn't read up on the bushmaster trials. Ballistic coefficient is best at 25mm, it was originally larger if I'm not mistaken. They neecked it down because the b/c was so much better that they needed less mass per payload to achieve what they wanted.

    • 4 weeks ago
      Anonymous

      Ballistic coefficient doesn't make a difference when your payload is HE. And caliber doesn't make a difference when your munition is a sub caliber dart.

      With a straight wall cased 40 mm you can have the same ammo capacity as 25 mm while lobbing big 25 mm grenades and shooting the exact same darts as you would with 25 mm

      • 4 weeks ago
        Anonymous

        Much to your surprise and chagrin, HE isn't the only kind of ammo. And your argument can simply be flipped. I could just load a 25mm HE in my 25mm instead of shoving it in a 40mm.

        Ballistic coefficient is just what you targeted as the strawman. So frick off you moronic Black person.

        • 4 weeks ago
          Anonymous

          >HE isn't the only kind of ammo
          Such as? Darts and HE both work better out of a 40 mm than a 25 mm with the HE particularly benefitting.
          >I could just load a 25mm HE in my 25mm instead of shoving it in a 40mm.
          Are you moronic? 25 mm has garbage payload compared to 40 mm.
          >Ballistic coefficient is just what you targeted
          Where? My point is to take 25 mm size cases, drop the shoulder, and shoot 40 mm HE with great payload and small darts out of it.

          • 4 weeks ago
            Anonymous

            The irony is that the large straight-walled case would actually be better for nearly any other kind of munition. If you wanted to make incendiary, smoke, giant meme shotshells for drones, etc, all that would be much better in 40mm.

            • 4 weeks ago
              Anonymous

              Exactly. Everything works great from 40 mm. Just have the darts and powder load be the same as in the 25 mm since that's enough and you end up with an extremely adaptable compact ammunition that you can carry in high volume.

          • 4 weeks ago
            Anonymous

            just a curious question. Does anybody know what kind of ammo US uses ex. in bradley? Is it APFSDS-T/HEI-T or do they use still APDS-T or just mix n match anything?

  3. 4 weeks ago
    Anonymous

    US might be going to straight walled 50mm rounds. considering how good we are at making IFVs, you should take note.

  4. 4 weeks ago
    Anonymous

    >making it straight walled so you can lob heavy big 40 mm grenades with low velocity and still shoot effective darts?

    Because then your darts aren't effective because they don't have enough propellant to go very fast.
    Also your big 40mm grenades will have really shitty ballistics and cripple the effective range of your cannon.

    • 4 weeks ago
      Anonymous

      If you take a 25 mm case and remove the shoulder your powder volume will be exactly the same as before.
      >Also your big 40mm grenades will have really shitty ballistics
      Who cares?
      >cripple the effective range of your cannon.
      With modern FCS your elevation is automatic so it doesn't matter if you're lobbing your rounds at 10° elevation and only 600 m/s you'll still be dead accurate and you'll still be constrained by your optics and detection range.

      • 4 weeks ago
        Anonymous

        >powder volume will be exactly the same as before
        Which now isn't nearly fricking enough because your bore's cross section is over 2.5x larger. You win the coveted 'moron of the day' award.

        • 4 weeks ago
          Anonymous

          Same amount of powder, same dart, why not the same velocity?

          • 4 weeks ago
            Anonymous

            Which part of
            >bore's cross section is over 2.5x larger
            did you not understand?

            • 4 weeks ago
              Anonymous

              What difference does that make?

              • 4 weeks ago
                Anonymous

                Pressure is measured in pounds per square inch. Larger bullets have more square inches to push against, so they get more pounds of force. This is the basic principle of the discarding sabot.

              • 4 weeks ago
                Anonymous

                More force sounds like a good thing though so what's the problem?

              • 4 weeks ago
                Anonymous

                The drawback would be that your barrel needs a 40mm bore instead of 25mm, which would make it significantly heavier most of the weight of a gun is in the barrel rather than the action, so you'll probably end up closer to 40mm weight than 25mm weight for the complete gun, which limits mounting options and means that you should probably consider moving up to a proper 40mm, which is substantially more powerful.

              • 4 weeks ago
                Anonymous

                >heavier. Most
                Fixed

              • 4 weeks ago
                Anonymous

                the new US 50mm weighs 660 pounds
                the Bushmaster 3 in 35mm weighs 480. so it's 180 pounds more, is that really all that much for an IFV?

              • 4 weeks ago
                Anonymous

                K40 is double the weight, but also gets you much more than double the power. The less powerful cartridge would make sense is recoil is a constraint for your vehicle though.

                Proper 40 mm has pathetic ammo capacity hence why straight walled 25 mm cases.
                >most of the weight of a gun is in the barrel rather than the actio
                This is not true actually, barrel is less than half of total in autocannons.
                Also, you could shorten the barrel length a bit due to the faster acceleration and also save a bit of weight in wall thickness since a larger diameter barrel is more rigid and rigidity and thermal mass are what actually drives barrel dimensions.

                So in total a gun designed for a straight walled case with a 40 mm bore would not be significantly heavier.

                >which is substantially more powerful.
                For what purpose? HE performance is the same and smaller darts are good enough.

                >For what purpose? HE performance is the same and smaller darts are good enough.
                You could lob HE much farther or fire the same saboted 25mm penetrators much faster.

              • 4 weeks ago
                Anonymous

                >You could lob HE much farther
                This is not true. Even with the reduced velocity you will still be limited by detection range, you will not run out of range, IFV's are conducting DIRECT FIRE missions, they are not artillery engaging targets 10 km away.
                >fire the same saboted 25mm penetrators much faster.
                For what purpose? This is the only benefit and in exchange you have 4x less ammo. What target are you engaging where 40mm (class) dart is required where 25mm (class) dart will not be sufficient?

              • 4 weeks ago
                Anonymous

                Proper 40 mm has pathetic ammo capacity hence why straight walled 25 mm cases.
                >most of the weight of a gun is in the barrel rather than the actio
                This is not true actually, barrel is less than half of total in autocannons.
                Also, you could shorten the barrel length a bit due to the faster acceleration and also save a bit of weight in wall thickness since a larger diameter barrel is more rigid and rigidity and thermal mass are what actually drives barrel dimensions.

                So in total a gun designed for a straight walled case with a 40 mm bore would not be significantly heavier.

                >which is substantially more powerful.
                For what purpose? HE performance is the same and smaller darts are good enough.

              • 4 weeks ago
                Anonymous

                f=m*a
                a=f/m
                f=P*A
                a=(P*A)/m
                A=pi*r^2
                a=(P*pi*r^2)/m
                if area increases faster than mass you get higher acceleration at a fixed pressure. higher acceleration means you either get higher velocity from a given barrel length or the same velocity from a shorter barrel.

              • 4 weeks ago
                Anonymous

                Seems like a good thing, so what's the problem with necking up 25mm cases and shooting darts meant for 25mm out of 40mm barrels with bigger sabots?

              • 4 weeks ago
                Anonymous

                nothing, except you might be better off with a 40mm(class) penetrator depending on how/if you want to modify barrel length. I think you may not be the person who was confused about this, but that post needed to be in the thread.

              • 4 weeks ago
                Anonymous

                The powder has to fill a significantly larger volume of space within the barrel.

          • 4 weeks ago
            Anonymous

            >same dart

            How do you fit the same dart in a 40mm bore without making the sabot proportionally larger, resulting in the same powder charge having to burn in a much larger volume while pushing against a heavier projectile offering more resistance, therefore imparting nowhere near the same velocity to the dart?
            Just stop typing you dumb frick.

            • 4 weeks ago
              Anonymous

              you get more area to push against. then you swap to a faster burn rate propellant. the sabot weighs less per unit area than the sabot, that's the whole point of a sabot.
              so for any larger area sabot you get higher acceleration for a given payload.

              • 4 weeks ago
                Anonymous

                >neck up a bottleneck round
                >use a larger diameter, heavier projectile
                >use the same powder load BUT a faster propellant

                I appreciate the dedication to the "mouth-breathing moron" act.

              • 4 weeks ago
                Anonymous

                >>use the same powder load BUT a faster propellant
                I assume you and he mean the same AMOUNT of powder, but a faster burning one, exactly how any sort of saboted projectile works. .50 BMG SLAP does not use the same powder as the standard ball load.

              • 4 weeks ago
                Anonymous

                .50 BMG SLAP is also considerably lighter than standard .50 ball. He's proposing the exact opposite: using a faster propellant for a heavier projectile, when 25mm APFSDS already uses a very fast propellant.

              • 4 weeks ago
                Anonymous

                >using a faster propellant for a heavier projectile,
                a heavier projectile WITH SIGNIFICANTLY GREATER SURFACE AREA.
                Projectile acceleration is a factor of pressure, projectile area and projectile mass. sabots weigh very little per unit area, as your sabot gets larger the projectile acceleration gets larger meaning you need a faster propellant to reach maximum pressure and full burn. this is nearly precisely analogous to reloading 5.56 vs. 350L. both have (nearly) the same case, but 350L bullets have lower sectional density (in this situation analogous to a sabot+projectile) the 350L bullet is WAY heavier (like, 2.5 times), but it uses faster powders (not even rifle powders anymore, but magnum pistol powders) because the increase of working area is so great. and even with that faster powder the peak pressure is lower than 5.56.

              • 4 weeks ago
                Anonymous

                >use a larger diameter, heavier projectile
                That's not what he's talking about though, he's talking about using a 25mm projectile in a 40mm sabot from a necked up 25x137 case.

              • 4 weeks ago
                Anonymous

                >>use a larger diameter, heavier projectile
                The dart is the same. The larger sabot doesn't add all that much weight.

    • 4 weeks ago
      Anonymous

      If you take a 25 mm case and remove the shoulder your powder volume will be exactly the same as before.
      >Also your big 40mm grenades will have really shitty ballistics
      Who cares?
      >cripple the effective range of your cannon.
      With modern FCS your elevation is automatic so it doesn't matter if you're lobbing your rounds at 10° elevation and only 600 m/s you'll still be dead accurate and you'll still be constrained by your optics and detection range.

      Here is comparison of 25x137mm and 27x145mm ammo. 27x145mm not exactly straightwalled but less bottlenecked than 25mm
      27mm has less case diameter.
      25mm HE is 186 grams
      25mm APFSDS M919 is 134 grams at 1420m/s. 135000 joules
      27mm HE is 260 grams
      27mm APDS is 260 grams at 1100m/s. 157000 joules
      So 27mm is more compact, larger HE, more powerful AP. There is no reason to use 25mm over 27mm.

      • 4 weeks ago
        Anonymous

        AP isn't just about joules of energy.

      • 4 weeks ago
        Anonymous

        Why not go straight for that 30x150? The physical size is almost the same while the payload is even better.

  5. 4 weeks ago
    Anonymous

    because most of those cartridges or their parents were designed before we figured that out

  6. 4 weeks ago
    Anonymous

    40mm for the win.

    • 4 weeks ago
      Anonymous

      The ejection is pretty kino

  7. 4 weeks ago
    Anonymous

    CT40 is superior to whatever the frick you just shat out trough your pipehole.

    • 4 weeks ago
      Anonymous

      It's too big.

      • 4 weeks ago
        Anonymous

        CTAi40 cannon is 320kg, it is extremely light for its class.
        And you don't need to use as much ammo as you would with 25mm cannon.

        • 4 weeks ago
          Anonymous

          It should be scaled to 25 mm size but firing the 40 mm projectiles. This way your IFV can carry +1000 rounds while having a light weight gun shooting 40mm HE and still having an effective APFSDS.

          • 4 weeks ago
            Anonymous

            ... what?

            • 4 weeks ago
              Anonymous

              Take a 25mm size class CT cartridge and use 40mm projectiles. That's the whole premise of this thread. Small case, big projectile, best of both worlds.

              • 4 weeks ago
                Anonymous

                A 25mm CT cartridge would be just over 25mm around. You couldn't fit a 40mm projectile in it.

              • 4 weeks ago
                Anonymous

                Just make it shorter and wider with the same volume.

  8. 4 weeks ago
    Anonymous

    >make the case telescoped and out of plastic.
    Telescopic is gay.
    Straight walls is the way.

  9. 4 weeks ago
    Anonymous

    I was on a Bradley variant and I’ve got to say frick the 25mm HE rounds. They suck shooting past like 1300m if you are moving they really blow. I don’t even want to think about how much heavier a 40mm gun would be. Not to mention the amount of ammo you could carry would be much less even if they happen to be more powerful. I’ll take the extra ammo and shit HE rounds over a more powerful gun. Just my take

    • 4 weeks ago
      Anonymous

      The whole point of this thread is the argument of combining the extra ammo of the 25mm with the effective HE of the 40mm by using a straight walled case that is similar size to the 25mm but uses 40mm projectiles.

      Honestly I guess I need to work on making my OP's more easy to read. Half of the people here completely misunderstood the premise even though it's literally in the first sentence.

      • 4 weeks ago
        Anonymous

        Ah good point. Got lost reading everyone’s shit that whatever OP said went out the window. Definitely could be interesting to see if they’d pull it off or not. As long as my fricking HE rounds don’t lob anymore than they do in all for it! Love the BFiST aside from its upkeep

        • 4 weeks ago
          Anonymous

          >As long as my fricking HE rounds don’t lob anymore than they do in all for it!
          They would be lower velocity so they would lob more. Your ranging is automatic so what's the problem?

          • 4 weeks ago
            Anonymous

            The ranging may be however it can still make moving targets very annoying to hit. Especially something fast like technicals

            • 4 weeks ago
              Anonymous

              Doesn't your FCS have automatic lead?
              I was honestly under the assumption that aiming was a solved issue in modern gun systems.

              • 4 weeks ago
                Anonymous

                It does and part of it is a skill issue on my end. As long as your vehicle you are tracking is moving at a constant speed and your gunner is competent enough to track in the same spots you tend to get hits. The issue comes when the target isn’t lased enough or the gunner pulls hard. They also have the gates but I’m yet to meet anyone that’s used it for anything aside from shits and giggles

              • 4 weeks ago
                Anonymous

                Do you think it might have something to do with the aiming controls? Whenever I've watched videos showing both gunner control and the aiming screen it looks like even a small movement causes huge turret movement and the gunner often overshoots the target. As if you were playing a game using huge mouse sensitivity and acceleration.

              • 4 weeks ago
                Anonymous

                Yeah small movements and really frick it up. It’s not bad until you zoom in though and are trying to hit a mover especially with a round like HE that takes a hot minute to actually reach its target

              • 4 weeks ago
                Anonymous

                This seems like a solvable problem considering how incredible aiming at pro level in video games is. Unironically the should just adopt mouse aim for vehicles.

              • 4 weeks ago
                Anonymous

                Cannot even imagine trying to use a mouse when that b***h is getting thrown all over the fricking place

              • 4 weeks ago
                Anonymous

                I guess it needs to be adapted for vehicles.

              • 4 weeks ago
                Anonymous

                Might just go full circle then

              • 4 weeks ago
                Anonymous

                No there's plenty of solutions that can be made to achieve fairly similar performance as the mouse while working in a moving vehicle.
                A couple of things, the amount of movement the user can make must be large so that he has more incremental control, this is why FPS players have low mouse sensitivity and large mousepads.
                Another thing is the type of movement, currently the aiming devices work like console controllers, where user input corresponds to movement speed in a direction, whereas with a mouse, user input corresponds to movement distance in a direction.

                So for example you could have controls that are similar in form to the current one but much wider for more accurate control and also work similarly to a mouse where you have to "lift" the mouse and move it back and forth to make the full circle.

      • 4 weeks ago
        Anonymous

        The main reasoning it isn't done more is that not only do straight walled cartridges burn the powder out faster which lowers velocity, but you have less case volume which reduces velocity. Most autocannon shells are unlike small arms cartridges in that they stuff the case basically to the top. This means any straight walled case is going to have a fairly significant drop in velocity over a bottlenecked one. It allows more HE but leads to much worse AP performance. For reference, I believe that the XM1203 50mm APFSDS is supposed to have similar or slightly worse penetration to 35mm APFSDS, but sacrifices velocity for this in order to achieve the same penetration and effect on target, making the range shorter. You effectively are trading AP performance for HE performance, which the US seems to think is worth it since few IFVs are resistant to 30mm APFSDS at combat ranges anyway

        • 4 weeks ago
          Anonymous

          How does this stuff work anyhow? You'd think that for a given powder load and barrel length the power would be fairly similar even with different calibers, no?

          • 4 weeks ago
            Anonymous

            It wouldn't because you get exponentially heavier projectiles as caliber increases. As an example for small arms, the standard bullet weight for .40 is 165gr, .357 SIG is 125gr despite only being 1mm narrower in diameter. With the same case capacity, the velocities when you load them to their pressure limits are about 1200 ft/sec and 1450 ft/sec respectively. 50mm is going to have a similar powder laid to 35mm but is going to be significantly heavier. You can technically lower the size of the projectile in the case of APFSDS to be the same as the 35mm APFSDS, but you run into larger sabot petals lowering peak velocity and also the straight walled case burning off the powder too quick which also lowers it even more.

        • 4 weeks ago
          Anonymous

          >It allows more HE but leads to much worse AP perfor...ACK!

          • 4 weeks ago
            Anonymous

            Lethality is not the same thing as penetration. A larger APFSDS dart will cause more post penetration effect than a smaller one, but will penetrate less armor due to lower velocities. It depends on the composite layout of the target as well but that generally holds

            • 4 weeks ago
              Anonymous

              >Lethality is not the same thing as penetration. A larger APFSDS dart will cause more po ... ACK!

              • 4 weeks ago
                Anonymous

                Why are you comparing an older 30mm penetrator that is shorter with a worse L/D ratio to a newer one that has a better one? Lengthen the 30mm one to be the same as the 40mm SS and it will have even better performance than the 40mm. This is the equivalent to saying that a 5.0 L engine is more fuel efficient than a 4.3 L engine because a 2024 Mustang gets better gas mileage than a 1965 Mustang

              • 4 weeks ago
                Anonymous

                Larger heavier penetrator = less velocity = less penetration

              • 4 weeks ago
                Anonymous

                L/D ratio takes precedence over velocity for penetrator armor defeat. Obviously if you have equally developed rounds with maximal allowed L/D ratios in the same case then the one going slower is going to penetrate less steel.

              • 4 weeks ago
                Anonymous

                40 mm in this picture doesn't have better L/D.

          • 4 weeks ago
            Anonymous

            >comic sans
            whoever put that deck together should be shot.

            • 4 weeks ago
              Anonymous

              it's far more common than it should be

          • 4 weeks ago
            Anonymous

            >Comic Sans

  10. 4 weeks ago
    Anonymous

    40mm CTA seems like overkill against anything that isn't a tank.
    Telescoped 35mm ammo would be a better idea.

    • 4 weeks ago
      Anonymous

      >anything that isn't a tank.

      what if you're shooting at the side of a tank? Being able to pen the side of a tank opens up a lot of options for an IFV.

      • 4 weeks ago
        Anonymous

        you are not penning any modern tank from the side with a 35mm.

        • 4 weeks ago
          Anonymous

          Do people in the current year still believe in fairy tales about "modern tank armor"?
          https://imgur.com/nude-hull-side-of-m-1-abrams-ONCuzkm

          • 4 weeks ago
            Anonymous

            hull side armor of the M1 is 2in steel with a 1in sideskirt
            the composite sideskirts being 5-layer steel/rubber armor

            this is enough to withstand RPG-7
            and 125mm rounds if at a steep angle, so even autocannon rounds wont penetrate until you are flanking

            • 4 weeks ago
              Anonymous

              If you had played Warthunder you would know how moronic what you just said is.

              • 4 weeks ago
                Anonymous

                we literally know this because the swedes tested it out
                125mm protection within a 50-degree frontal arc and RPG-7 protection within a 90-degree frontal arc on the hull
                30mm cannon rounds would need to be near-perpendicular to penetrate the side hull, at least beyond a 50 degree frontal arc

              • 4 weeks ago
                Anonymous

                so what caliber autocannon would be needed to penetrate reliably NOT from a perpendicular angle?

            • 4 weeks ago
              Anonymous

              Hull isn't covered with heavy side skirts completely, rear part skirts are just sheet metal, so around engine it's just 1-2" steel plus standoff skirt.
              Also Chobham armor is not so hot against KE.

  11. 4 weeks ago
    Anonymous

    >/k/ doesn't know why necked cartridges are used in general over straightwalls
    JFC the state of this board.
    >smaller action length
    >smaller oal
    >in order to maintain the same velocity of a 25mm in a straightwall the length would have to increase dramatically
    >better lockup and sealing in chamber
    >straightwalls are only preferred in low pressure or heavy grain projectiles where maximizing speed does not matter(like 40mm grenades/9mm/.45/etc)
    >ease of loading, makes autoloaders or any action a lot more consistent and reliable

    • 4 weeks ago
      Anonymous

      >>in order to maintain the same velocity of a 25mm in a straightwall the length would have to increase dramatically

      https://i.imgur.com/oaKEPYA.jpeg

      [...]
      Here is comparison of 25x137mm and 27x145mm ammo. 27x145mm not exactly straightwalled but less bottlenecked than 25mm
      27mm has less case diameter.
      25mm HE is 186 grams
      25mm APFSDS M919 is 134 grams at 1420m/s. 135000 joules
      27mm HE is 260 grams
      27mm APDS is 260 grams at 1100m/s. 157000 joules
      So 27mm is more compact, larger HE, more powerful AP. There is no reason to use 25mm over 27mm.

      • 4 weeks ago
        Anonymous

        Are you genuinely moronic?
        I'm talking about straightwalling, as is op.
        Yes, even if a round is shorter, if it has a wider case, it'll carry more grain for the power and you can fit larger bullets, due to the necked design, which is exactly what I fricking talked about.
        >not exactly straight walled
        it's a necked cartridge, just a high neck which is where the extra powder comes from. if you took that 27mm and made it a true straightwall, it'd be a good bit longer due to inverse cube law(in this case cylinder).
        I'm not arguing the 27mm is worse(in my opinion it's a superior round for most instances), I'm explaining the fundamental design choices of why they're necked.

    • 4 weeks ago
      Anonymous

      https://i.imgur.com/Ji2aUIi.jpeg

      Are you genuinely moronic?
      I'm talking about straightwalling, as is op.
      Yes, even if a round is shorter, if it has a wider case, it'll carry more grain for the power and you can fit larger bullets, due to the necked design, which is exactly what I fricking talked about.
      >not exactly straight walled
      it's a necked cartridge, just a high neck which is where the extra powder comes from. if you took that 27mm and made it a true straightwall, it'd be a good bit longer due to inverse cube law(in this case cylinder).
      I'm not arguing the 27mm is worse(in my opinion it's a superior round for most instances), I'm explaining the fundamental design choices of why they're necked.

      >>in order to maintain the same velocity of a 25mm in a straightwall the length would have to increase dramatically
      The whole point of this thread was to propose accepting the velocity hit of a heavier projectile in exchange for heavier HE payload in the 25mm case size category. Darts should still works fine though the sabot will weigh a bit more.
      >>ease of loading, makes autoloaders or any action a lot more consistent and reliable
      This is bullshit, it either makes no different or is better for non shouldered cases.

      I swear you people CANNOT read.

      • 4 weeks ago
        Anonymous

        >This is bullshit, it either makes no different or is better for non shouldered cases.
        Alright now I know you're moronic, there's a reason why all automatic at larger calibers and autoload actions prefer and use necked cartridges. You can get straightwalls to load as well but you need to compromise on one of the following:
        >shell design, going very long creates a large momentum arm and can bind in feeding, even more so with debris
        >breach, either longer or wider to fit a larger diameter feed ramp
        >projectile design. nothing sharp can be forward, it must be a round nose or rounded to help facilitate the feeding, or if flat requires a curled/rolled edge(think shotgun shells)
        These issues aren't as present on small calibers due to those reasons. Once you scale up, the compromises start to suck.
        Again I'm specifically answering this question from

        https://i.imgur.com/yO5Q2nj.jpeg

        Why do IFV's use necked cartridges?

        It doesn't make sense to me. An IFV wants to have a large caliber HE shell for infantry etc. and a sub caliber dart for armored targets.

        So why isn't everyone just taking the small 25 mm shell that you can carry a frickton of and making it straight walled so you can lob heavy big 40 mm grenades with low velocity and still shoot effective darts?

        That would be the best of both worlds, good payload, good ammo capacity, and good penetration, and while you're at it, make the case telescoped and out of plastic.

        >Why do IFV's use necked cartridges?
        Outside of the issues I've listed, having slower HE sucks ass, one of the best uses for the bradley is accurate and rapid hits on 1km targets. Once you start going low velocity, you basically neuter the system and it's purpose.
        >well just carry the high velo he
        then it makes the whole purpose moot.

        • 4 weeks ago
          Anonymous

          > there's a reason why all automatic at larger calibers and autoload actions prefer and use necked cartridges
          Yes that is because they need the powder load
          design, going very long creates a large momentum arm and can bind in feeding, even more so with debris
          You are being intentionally dishonest, we are talking about THE SAME SIZE CARTRIDGE
          , either longer or wider to fit a larger diameter feed ramp
          Again
          design. nothing sharp can be forward, it must be a round nose or rounded to help facilitate the feeding, or if flat requires a curled/rolled edge(think shotgun shells)
          What in the world are you talking about?
          >having slower HE sucks ass, one of the best uses for the bradley is accurate and rapid hits on 1km targets.
          Why is this an issue with modern FCS's that can automate lead and tanging? Does it really make a difference if your round is traveling 900 m/s or 500 m/s? Do consider that we are talking about more than doubling the payload at the same ammo capacity.
          >>well just carry the high velo he
          I've never said that

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