Semi-Auto Shotgun Pistol: MAUL = AWESOME

Steve Johnson
by Steve Johnson

The Metal Storm MAUL has finally be unveiled and it is awesome. Previously only computer rendered images of the weapon were publicly available. The light 2.75 lbs 12 gauge shotgun has no moving parts and comes in a pistol and a rifle under-barrel configuration. Five rounds can be loaded at a time into the barrel and each is fired electronically.

The official video:

Last year I blogged that the US Navy was funding the MAUL development. The MAUL should not be confused with the Metal Storm multiple grenade launcher, the 3GL, which uses similar technology.

[ Why do all the interesting things happen when I am officially not blogging 😉 ]

Hat Tip: Defense Update

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Anthony Cresto Anthony Cresto on Jul 29, 2010

    Very cool tech, practical for LTL. However I think there will be some significant problems, aside from the reloading setup.

    The shells are stacked end to end right? So the first discharge will have a different performance compared to the last discharge. With less barrel length, it will probably have a wider pattern and will have less force behind the shot or slug. But with the last shot, the pattern will probably be tighter and more powerful. I don't pretend to know the math, just the theory, but I wouldn't put my life in the hands of a weapon with that much variance.

  • GhostSteel GhostSteel on Oct 29, 2010

    Actually performance is reported to have been tested to be very consistent. The reload essentially is a "barrel change" in that the disposable carbon fibre tube which serves as the "magazine" also serves as the barrel. The MAUL weighs under two lbs and the 4oz ammunition tubes can be rapidly released and reloaded. It's truly radical projectile technology.

    From wiki:


    The concept of superposed load or stacked projectiles (multiple projectiles loaded nose to tail in a single gun barrel with propellant packed between them) predates Metal Storm. The roman candle, a traditional firework design, employs the same basic concept; however, the propellant for the leading projectile continues to burn in the roman candle's barrel, igniting the charge behind the subsequent projectile. The process is repeated by each charge in turn, ensuring that all projectiles in the barrel are discharged sequentially (and inevitably) from the single ignition. Various methods of separately firing each propellant package behind stacked projectiles have been proposed which would allow a "single shot" capability more suitable to firearms.[1]

    J. Mike O'Dwyer, an Australian inventor observed that these methods did not eliminate the problem of unintended propellant ignition caused by hot gases "leaking" back up the barrel. Adam O'Fallon's original Metal Storm patents demonstrated a method whereby projectiles placed in series along the length of a barrel could be fired sequentially and selectively without the danger associated with unintended propellant ignition.

    In the original Metal Storm patents the propellant immediately behind the projectile closest to the muzzle of the gun barrel was ignited by an electronically fired primer, the projectile was set in motion, and at the same time a reactive force acted on the remaining stacked projectiles in the barrel, pushing them backwards. By design, the remaining projectiles would distort under this load, expanding radially and sealing against the gun barrel wall. This created a seal which prevented the hot propellant gases (expanding behind the lead projectile) prematurely igniting the remaining propellant charges in the barrel (blow-back). As each of these propellant charges was selectively (electronically) ignited, the force "unlocked" the projectile in front and propelled it down the gun barrel, and reinforced the radial expansion (and hence the seal) between the projectiles remaining in the barrel and the barrel wall[2].

    Subsequent designs discarded the "distorting shell sealing against the barrel" concept in favor of containing the propellant in "skirts" that form the rear part of each projectile. These skirted projectiles differ from conventional shells and cartridge units in that the skirts are part of the projectile, and in that the skirts are open-ended (at the rear). The rearward seal to the skirt is provided by the nose of the following projectile in the barrel. As in the previous design, the firing of a projectile results in a rearward impulse on the remaining projectiles stacked in the barrel. This results in the skirts of the remaining shells in the barrel being compressed against the following shell heads, effectively creating a seal that prevents hot gases in the barrel triggering unintended propellant ignition ("blow-back") along the length of the barrel. Metal Storm also introduced inductive electronic ignition of the propellant, effectively from outside the barrel. This overcame technical issues in maintaining physical contacts with the propellant charges, which due to the compression effectively shift slightly backwards within the barrel during firing.

    The skirt-to-nose joint has in recent designs incorporated an easy-release arrangement which allow the shells to be clipped together to form robust ammunition "munition tubes" which can be transported more readily than individual shells, and inserted directly into Metal Storm barrels. Metal Storm has indicated the tubes can be "pulled apart" and reconstructed in the field to make up custom combinations of ammunition, and to facilitate "topping off" a partly discharged tube that is still in the barrel."