Guns Using Cased, Telescoped Ammunition


AAI Corp continues to develop caseless, telescoped ammunition and machine guns to fire it under the United States Joint Service Small Arms Research Program Office’s (JSSAP) Lightweight Small Arms Technologies (LSAT) program.  The caseless, telescoped ammo and gun developed by AAI under this program, was first mentioned at The Firearm Blog in 2010.


In a parallel development program, the company developed a polymer cased, telescoped round.  The cased round is a “full polymer cartridge” that claims a 40% weight reduction when compared to metal cased ammo.  The rounds also feature a 12% volume reduction, meaning the same sized pouch will carry more ammo and still be lighter than conventional ammunition.

According to AAI, more than 50,000 of the cased, telescoped rounds have been fired.  Presumably, this includes the US Army 2011 testing.

LSAT folding

AAI has two belt-fed guns, one a full size machine gun comprable to the M249, and a second compact variant with a short barrel and folding stock.  The company states the guns use a rotating chamber to “…[provide] in-line, push-through feed and ejection…”

Currently, the cased, telescoped ammo is in 5.56mm, and the same technologies are being used to develop a 7.62mm round.

Richard Johnson

An advocate of gun proliferation zones, Richard is a long time shooter, former cop and internet entrepreneur. Among the many places he calls home is


  • This is voodoo black magic. Someone call a priest.

  • Mystick

    Ejection of what? I thought it was caseless….

    • Dave

      belt links, they are not held together by magic

      • Mystick

        My understanding was that stripping the link was accomplished on the feed stroke, not the ejection stroke… otherwise the cartridge could not be inserted into the breech.

        • Ripley

          Basically in “in-line, push-through feed and ejection” the feed, chambering and ejection happens at the same time in one motion, and then the chamber rotates in line with the barrel much like a one chamber revolver.

    • Giolli Joker

      There are two system under evaluation… CTA (cased telescoped ammo) and caseless, the former has a polymer case, hence ejection, and it should be in phase 7 of the evaluation process, the latter is completely caseless but its development is in an earlier stage.
      I believe that CTA is the way to go in the medium to long term, I just hope they’ll settle for something around 6.5mm (maybe with Grendel-ish ballistics) instead of sticking to 5.56…
      I think that such design in the civilian market would make GREAT hunting revolvers too…

  • steef

    Links perhaps ?

  • bbmg

    AAI deserve a lot of respect for genuine firearm innovation, something that they’ve been doing for a long time:

    I doubt the issues with the caseless ammunition will be surmounted in the near future but the polymer cases certainly seem to hold a lot of promise. This is the sort of development that will give individual soldies a clear advantage on the battlefield, not another rehash of the AR platform shooting ammunition that was designed long before most of the people using it were born.

    • Ian

      Except that very little here is innovative. Case telescoped ammunition has been around for decades and decades.

      And it causes more problems than it solves.

      • Giolli Joker

        Other than 40mm CTA…

        • Raven


          • Beaumont

            Not telescoped. The bullet is simply seated below the cartridge rim.

          • Giolli Joker

            Yep, the 7.62x38R isn’t more telescoped than a .38 wadcutter…
            Two examples I can think about are KAC silent ammunition for their silent revolver (based on .357) and silent rifle (based on .44Mag), they were truly telescopic but they were even employing an internal piston (like similar soviet ammo) to seal in the gasses… I don’t think many samples have been produced.
            As far as I know, a CTA has a cylindrical shell that hides a smaller diameter projectile, completely encased and sorrounded by the charge, a starter charge pushes the ball in the throat of the barrel and then the main charge is ignited.
            I can’t deny that out there there might be many different examples and prototypes, but I would argue that aside 40mm CTA and the one of LSAT, none of them has been or is being widely tested and developed.
            One of the issues at the moment is pretty sure manufacturing cost…

    • Komrad

      H&K and Dynamit Nobel already solved all the issues.

      • Kirk

        Really? Then I wonder why AAI can’t seem to make it work, since they bought the technology from those two companies.

        The G11 was never able to live up to its hype. The test versions here in the US for the ACR program had issues with propellant stability, chamber sealing, and gas cutting at the seals. Given that those weapons were supposedly “product improved” after the Germans decided to cease development on the G11, I’ll have to infer that the basic problems with the concept were never solved by HK, and that AAI bought a pig in a poke when they purchased the supposed “off-the-shelf” technology.

    • dp

      One step remaining to make it useable for “individual soldier” as you say: make it useable in rifle. I am afraid a rifle 9refering to feed mech.) that expensive is simply out of viable prospect. It is highly unlikely, they will make it a general or even limited issue ammo without having rifle for it.

  • steef

    yeah maybe in 10 or 15 years this will all be commonplace, especially polymer case

  • Lolinski

    When this hits the market “survivalists” will debate the reloadability vs weight of brass and polymer ammunition, respectively

  • Thatguy96

    Just to note LSAT was renamed Lightweight Small Arms Systems (LSAS) in FY12 and was subsequently canceled in the proposed FY14 budget (no funding allocated). The JSSAP announced in the FY14 budget proposal a desire to yet again investigate a “universal projectile concept.” This might leverage development from the LSAT/LSAS program, especially since part of the reason that the LSAS program was canned was dissatisfaction with the fact that it was still using a 5.56mm bullet, but that’s unclear. Its also an RDT&E effort, so like LSAS, it might not go anywhere.

  • Flyingchipmunk

    I think polymer cased ammunition is a cool idea and the weight savings would be a great thing for military GIs. However my only experience with plastic cased ammunition was a guy in the slot next to me at a range using it, and having every other shot fail to eject. One thing people usually dont discuss is how he brass cases of traditional cartridges suck a lot of the heat out of the action and keep the gun a lot cooler. Synthetics would have a problem taking the heat out of the system leaving the action quite hot, which combined with their tendency to melt makes for a sticky situation (pun intended). I believe with time this can be improved though and everything has to go through its paces to reach perfect usability.

  • dp

    Talking case-less, huh?!

    Here it is – year of introduction is 1848.
    The Austrians figured pretty quick how it works during war of 1866-67.

  • Nathaniel

    The cased telescoped ammo has some real issues.

  • Brandon

    I find telescoped and caseless ammunition to be a very interesting concept, and would enjoy more blog posts on the subject.

    Up vote if you agree.
    Down vote if you disagree and would like more zombie themed special edition blog posts.

    • RobGR

      How about both?

  • Leigh Rich

    When i was stationed at Rodman Labs at Rock island Arsenal in the 70’s they were expermenting with caseless ammo back then. Wonder if it will ever be reality..