Ultra Autocannon

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Ultra autocannon

The Ultra autocannon was an advanced variation of the standard autocannon, with the ability to fire at twice the normal rate.


The Ultra autocannon technology was originally developed by Kawabata Weapons Industries, in the form of a specialized autocannon/5, specifically for use by Defiance Industries's new Sentinel BattleMech design.[1] In order to improve upon the standard autocannon's already-prodigious rate of fire, the engineers chose a magnetic loading system which could feed rounds into the firing chamber much faster than mechanical methods; this also necessitated the use of ammunition which contained highly magnetic material. The rounds were further enhanced with the use of a new aluminum/foamed titanium alloy which made them lighter and hence achieved superior muzzle velocities over standard ammunition.[2] The result was a weapon that resembled a normal autocannon—with a shorter, smooth-bore barrel—but had a superior effective range compared to standard AC/5s or LRMs and could operate at either normal or double the rate of fire.[1][3]

While these enhancements made the Ultra AC/5 a superior weapon, it was only after it began to see battlefield use that several problems emerged. Although it could achieve a comparable rate of fire, the Ultra AC/5 was not as accurate as paired AC/5s mounted together. Additionally, besides burning through ammunition more quickly and generating more waste heat, operating the Ultra AC/5 at its maximum rate caused the weapon to vibrate violently, potentially causing internal damage to the 'Mech carrying it without sufficient precautions.[1] The most damning flaw in the weapon though was its magnetic firing mechanism which, after sustained periods of rapid fire, would experience thermal expansion and fuse a round in the firing chamber. Many MechWarriors balked at the notion of a weapon which could be rendered useless for the rest of a fight and chose to stick with standard autocannons. Due to this flaw in its design, security around the Ultra technology was neglected, allowing other companies to acquire it and build versions of their own, while for the same reason no attempts were made to develop different calibers of Ultra autocannons.[2]

Like many pieces of advanced Star League technology, Kawabata and their unique weapons disappeared during the maelstrom of the Succession Wars, though the Clans retained and refined the technology, eventually producing variants in all autocannon classes. Thanks to the Helm Memory Core, the Successor States regained the ability to produce the original Ultra AC/5 in 3035.[4] Using this weapon and Clan-tech salvage, Inner Sphere scientists were eventually able to introduce Ultra versions of the AC/2 and AC/10 in 3057, and finally the AC/20 in 3060.[5]

Ultra autocannons were also effective against multiple targets, when single bursts of fire were "walked" up to each opponent.[6]

See Also[edit]

For specifics about a particular type, click on one of the links below:


  • This article refers to a common object and addresses the object as a common noun. The preferred term is "Ultra autocannon" or "UAC" (except on section titles & table headings, where "Ultra Autocannon" is favored). When addressed by class, the preferred terms are "Ultra AC/5" and "UAC/5" (et al.).


  1. 1.0 1.1 1.2 Technical Readout: 2750, p. 26: "STN-3L Sentinel"
  2. 2.0 2.1 Era Report: 2750, p. 98
  3. Technical Readout: 2750, p. 7
  4. Technical Readout: 3050, p. 215
  5. Tactical Handbook, p. 55
  6. Tactical Operations, p. 100: "Autocannons"