.50 Caliber All-Purpose SABOT Ammunition in Development by US Army ARDEC [NDIA 2017]

The US Army Armament Research, Development and Engineering Center (ARDEC) is developing a new kind of .50 caliber ammunition called the All Purpose Tactical Cartridge, according to a presentation given at this years National Defense Industry Association small arms conference. The new round will be a sabot design, similar to the existing .50 cal M903 SLAP round, but apparently with a more streamlined shape and better accuracy.

Recently, Senators as part of the Senate Armed Services Committee questioned Army Chief of Staff General Mark Milley about the need to penetrate advanced body armors which are now coming to market in increasingly large numbers. A smaller caliber round similar to the All-Purpose Tactical Cartridge which fires a hardened projectile at very high velocity using a sabot to improve efficiency could be just what is needed to fill this role, and potentially could do so without the use of expensive tungsten material. While the APTC is much larger than would be necessary, proving the technology with a .50 caliber round could be the first step towards its application in a smaller caliber round. Notably, the project plans to combine the sabot projectile design with lightweight composite cases, already troop-tested via the Mk. 323 Mod 0, which should result in very lightweight ammunition relative to other .50 caliber rounds. Potentially, this could allow the new APTC to function as a powerful anti-armor force multiplier for light vehicles, if coupled with a lightweight .50 caliber machine gun. The round is also said to incorporate One-Way Luminescent (OWL) tracer technology.

The new round is slated to complete engineering and manufacturing development, the last step before fielding, by the 1st quarter of 2023.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Alexander Nguyen

    …I didn’t realize .50 cal isn’t adequate for defeating cheap hard armor…seriously? Or am I understanding this wrong, is this for a different weapons platform? 5-7 round burst at 2400m sounds like an HMG…

    • Sorry, the wording in the middle is a little confusing for what I was trying to say. Gimme a minute.

    • Aaaand, done. Should make more sense now.

    • Mikeadri

      Maybe NOW its adequate but in 10 years?? Thet most expensive body armors nowadays are capable of stopping 50 cal m2 ap. In 10 years even cheap chinesse plate maybe capable also… Look its meant to enter service in 2013…

      • Mieadri

        2023 sorry

  • Giolli Joker

    Very interesting, I’m curious about ballistic data.

  • Major Tom

    There’s wearable body armor capable of withstanding .50 cal?

    • jono102

      The Brits had some in Northern Ireland in the late 80’s/early 90’s. The IRA were getting 50 cal rifles incl Barretts from the US to take pot shots from at patrols especially around the border areas. They developed the armor around that. Issue was the reduction in mobility with the heavier armor, especially on rural patrols. Talking to a Brit the biggest issue the soldiers saw was the fact it may not penetrate the armor but the energy it still dumped into the target would mess you up internally pretty well. Instead they just tried to avoid the areas.

      • MeaCulpa

        Aaah post 9/11 IRA funding and arms supplies seemed to dry up for som reason.

        • jono102

          It was dying down a while before then. Support from various elements was already drying up especially when it was proving easier to trace financial support to its provider. By that time it was mostly just the few die hard’s who didn’t want to go to the negotiating table. Their political “brothers” quickly distanced themselves from them too. 9/11 just made them less attractive to associate with.

  • Brett baker

    DOD news release June 30,2024: Recent intelligence indicates Russian and Chinese troops are being issued body armor that will withstand the .50 APTC.

    • Mikeadri

      To be honest this is very likelly.. maybe not in 2024 but 2029 this maybe very true…
      Technollogy goes so fast that its amazing !!!

  • roguetechie

    The age of the sabot is upon us…

    • ostiariusalpha

      Plastic case-telescoped and sabots go together like peanut butter and chocolate. If it wasn’t for having to deal with feed ramps, I’d say that even all conventionally designed small arms should be chambered for sabot rounds, they just make everything better. Except flechettes, those are a headache to engineer a proper sabot around without stretching the cartridge out to a short action length.

      • roguetechie

        To an extent modern manufacturing technology, and the research done by cbj tech ab into sabot design shows that even conventional cased and bottlenecked sabot rounds are very possible to get right at this point.

        But yeah, saboted CT is gonna be awesome!

      • Jan Moszczuk

        If what you say about sabots and CT is true, then why Steyr ACR failed? Why flechettes are such a problem?

        • Uthýr

          Flechette = extremly high velocity, and thin = needs a big sabot… that is heavy. And due to kinetic energy scaling squared with velocity such a sabot takes up a stupid amount of energy. Also theyr hard to get accurate.

          But at the end the biggest downside is low supression, and most rounds shot are supressive fire anyways

        • ostiariusalpha

          Flechettes are very long for their caliber; this makes it difficult to use cup sabots, which would eat up the powder volume in the case. The Steyr ACR and SPIW programs tried to get around this by clasping the flechette around its nose instead; this type of sabot is very difficult to get a clean, consistent separation from the projectile, leading to serious shortcomings in ballistic precision that are not a problem for cup-type sabots. Uthýr isn’t right about the sabot weight, but the reduced suppression effect is correct. The sabots they used were plastic, so weight-wise they were still much lighter than conventional bullets; in fact, these flechettes extreme (+4000ft/s) velocities were the product of their light weight making them easy to accelerate. The sound of a supersonic crack has multiple factors affecting its audible volume: one is the length of the supersonic body, so the longer flechette has more potential “noise” than a shorter conventional bullet; but the more important factor is how close to the transonic barrier a traveling body is moving, a faster projectile has a tighter shockwave cone that leaves less space for the creation of acoustic waves. This means that the hypervelocity of the flechette makes it a bit less loud than the slower conventional bullet; though it would still be plenty noticeable if one zipped by your head.

          • Uthýr

            Im right, most sabots even tough theyr “light” are actually stupidly heavy in relation to the flechette and for the velocity, as said energy scales with velocity squared, a “light” sabot will waste a ton of energy.

            One of the things further, is you want the center of pressure rather to the rear for stabilisation. So you need a really fine nose which further decreases the shock cone, additional to its narrow angle.

          • ostiariusalpha

            The spindle sabots used in the SPIW and ACR were not particularly weight efficient designs, but the ACR nylon sabot assembly still only weighed 0.5 grams, compared to the flechettes’ 0.64g.
            https://uploads.disquscdn.com/images/b8b10f33081524db11b258bbbc4de1a2922dc2e22585958754d6d836771b1586.jpg
            https://uploads.disquscdn.com/images/d517ef81097e59615d3cdaf69aba732be74f18a1821399375fdcc10bd191b35c.jpg
            You are correct again about the stabilization and nose angle.

          • Uthýr

            You see thats 569 JOULE, compared to 729 to 738 Joule of the Projectile. 43,5% (almost half) is used just for the sabot.

            Thats the thing, due to flechetts beeing thin, the sabots have to seal more area, and due to the extrem velocity, theyr weight matters much more than it seems.

          • ostiariusalpha

            I don’t think it’s as terrible as you’re making it out to be, but I see your point. That 43.5% energy loss could definitely stand some improvement. Then again, that’s why I prefer pairing efficient form factor bullets with cup sabots over flechettes, like the 5mm 5g projectile I keep touting; the weight ratio is far better.

          • Uthýr

            Have fun pressing 5gramm into 5mm without rare and expensive tungsten…

          • ostiariusalpha

            ???
            It’s pretty easy, you simply make the bullet longer.
            https://uploads.disquscdn.com/images/b58505a2a300362fd203df2de1cb66d7a396a9e740782fc7dbe120444faafaaa.jpg

            Edit: Oops! I meant 4g, not 5g. 😅

          • Uthýr

            Yes, even tough the “simpler” part isnt that simple, the big problem is that projectiles scale NOT just as the usual known w1:(d1 : d2)³ ,a smaller diameter will have much more stabilisation problems and therefore be even shorter in relation. With EPR projectiles you also cant just tighten the twist as you like, it will otherwise rip appart verry quick.

            With the EPR density it gets really hard to put 4gramm into 5mm… My calculator says a big no to it. The twist needed rips appart the jacked.

            Also the nose of this pic sucks hard. It will perform rather poor.

          • ostiariusalpha

            You’re forgetting that higher velocity bullets need less twist to be stable. You also are ignoring that bullet jackets are regularly designed to handle the centripedal force of higher velocities. Using standard Tombac and gilding metal alloys would be foolish, because even if they didn’t rip off from the rapid spin, they would peel off too early during the terminal phase. Instead, using a coated steel jacket would be ideal; especially since only the sabot touches the bore of the barrel rather than the bullet itself, so there’s no increased wear. You should probably justify your comment on the nose, how exactly does it “suck hard” to you?

          • Uthýr

            A thicker or tougher jacked greatly reduces your fragmentation range, to a certain point the ballistic advantage nullifies a bit but then becomes negative. In general you simply have material restrains when it comes to twist rate.

            And no im not forgetting it – but you kinda seem to forget that you still need to a proper twist for it to be stable at lower velocitys at range.

            The nose is shaped extremly poor. Besides that the bearing is long for no good reason, 2calibers is senceless.

          • ostiariusalpha

            The bullet’s bearing surface is irrelevant, it sits in a sabot. It only looks that way to balance the mass of the separate penetrator and core. As for the fragmentation range, the mild steel jacket will strip off quite well at 600m; which is all I require it to do. By the time the projectile reaches a low enough velocity to become unstable again, it will have gone rather far past its effective combat range (i.e. where an infantryman can be expected to make a hit even with a magnified optic), so that’s also irrelevant.

          • Uthýr

            Well ok, im more interested to also use the round in LMG’s where this just doesnt fit in supression range therms.

            Supression (supersonic crack) still is quite usefull over the effective combat range.

          • ostiariusalpha

            I consider LMGs to be more appropriate for <800m combat. Any further out and you should be using a MMG chambered for a more powerful cartridge with a larger caliber bullet.

          • Uthýr

            Or just use a god damn actually efficient projectile….. to much math right…?

          • ostiariusalpha

            More power and larger caliber are relative terms, no one said the projectile couldn’t be more efficient.

      • I would think that the fundamental issue of flechettes having crapulous terminal ballistics has more to do with why they’ve never been large-scale adopted for small arms than any engineering difficulties associated with getting them to the target. APFSDS has so far been the only practically effective use of “flechettes”.

        • Uthýr

          They fishhook in flesh, Hint: 5000fps do hurt

          • It speaks volumes that when googling around for [flechette terminal ballistics], the one thing that almost every page extolling the wounding potential of flechettes has in common is that they’re trying to sell you something.

          • ostiariusalpha

            How is that different from any other projectile? The SPIW test results came from an Army ordnance lab, not the manufacturer.

        • ostiariusalpha

          While it lacked the fragmentation capabilities of M193, the ACR flechette had spectacular terminal effects due to its tremendous velocity. Unlike the dismally inadequate performance of the M546 APERS-T artillery flechettes that topped out at 1800ft/s, the Steyr flechette had excellent barrier penetration and consistent buckling and tumbling in tissue similants with large wound channels at 4757ft/s.

      • Renato H M de Oliveira

        Flechettes don’t scale down well.
        That’s why there are no mass deployed flechettes under 25mm – they are utterly ineffective.
        It was the main reason for the failure of SPIW.

        • ostiariusalpha

          That gets said a lot, but it doesn’t square at all with the documented facts. In Army testing of flechettes at a wide spectrum of velocities, the flechettes performed excellently in both penetration and terminal effects from 850m/s and up, with the Steyr ACR’s flechette being beyond impressive at 1450m/s. The evaluation documents show that it really was the insurmountable precision difficulties that killed both the SPIW program and the Steyr ACR.

          • Renato H M de Oliveira

            That’s part of the “scale down” thingie.
            And small flechettes don’t fare that well when facing hardened armour, Level IV style.
            One could suspect that if they were so spectacular someone, somewhere would mass issue them, at least in machine guns, where pinpoint accuracy isn’t such a must have.

          • Simple

            Why then use low energy flechettes to begin with… Just pump them to 2400Joule and they wreck stuff.

            2mm Flechette with 2400J = 763,9 J/mm² !!
            While 7.62×51 is 69 J/mm² ….

            = 1100% the KE/mm² …….

          • Renato H M de Oliveira

            Given the low energy efficiency of saboted vs full caliber rounds, to put 2400 J on a flechette you’d need at least a 7.62×51.
            That defeats the “small, light” thingie.
            But that energy density is exactly what makes flechettes so attractive for AP.

  • Jan Moszczuk

    Accurate saboted projectiles? I hope it will trickle down to smaller calibers. A sabot would solve 6.5CT’s recoil problem

  • Kevin Gross

    Needs to be a metal sabot, one that is half the tensile strength of the core. When penetration occurs, to keep the core from disintegrating from rearward to front, you need something to hold the penetrator together. Why build something that’s going to take 6 years, when you all ready have same product on the open market already? What’s wrong with CheyTac, DSG, Silver State Armory, or Beck Ammo. Rheinmetall Defense already just announced their RMG with APDS rounds in 12.7×99.