BattleMech Weapons

Autocannon:
Machine Guns with a Kick

by Precentor Janos Abu Hassan

Autocannons are descended from the rapid-fire, explosive warhead rounds first developed for use against aircraft and armor during the mid-20th Century, which, in tu m , were developed from the 19th century Gatling machine gun. Indeed, many hightech, 20th and 21st century autocannon types were based directly on the rotating, multi-barrel designs developed in Gatling's original design.

BattleMech autocannon are rapid-fire weapons ranging from 40 to 120 mm, firing shells designed to cause the maximum damage to BattleMech composite armor. Shells are fed into the autocannon's firing chamberfrom a shell cassette, inaccurately labelled a "round." BattleMech AC ammunition inventories refer to the numbers of "rounds"-i.e., cassettes holding anywhere from 4 to 100 individual rounds, or shellsstored aboard. The number of shells in a cassette depends on the caliber of the shell and on the design of the cannon. Some weapons eject spent cassettes almost as fast as empty cartridge casings-but the cassette system allows fresh rounds to be smoothly and automatically chambered to a weapon which is often (e.g., the MAID-3R Maraude6 not an integral part of the BattleMech's hull.

Autocannon effective range depends on the size of the weapon and on the caliber of the shell fired. Autocannons are classified by the number of cassette "rounds" which can be fired within 1 0-seconds, though this can be misleading since there are fewer shells in large-caliber cassette rounds than in smaller. Generally speaking, autocannons firing a large number of small shells from cassettes holding a large number of shells (the AC/2, for example) have a longer range but cause less damage than heavier shells fired in short bursts from cassettes holding only a few rounds (such as the heavy AC/20).

The characteristics of each autocannon type are listed below:

AC/2: The AC/2 is a relatively light weapon (about 6 tons) which causes relatively light damage for a weapon of its size. It has an extremely high rate of fire, with a sound which has been likened to a buzzsaw. The AC/2 has an effective range of over700 meters but is prone to difficulties in targeting at ranges of less than 120 meters. The high rate of fire causes maintenance problems as well, necessitating frequent relinings of the barrel.

The BJ-11 Blackjack mounts an AC/2 in each arm as main weapons in its primary mission as a source of sup-pression fire against non-'Mech forces.

AC/5: The AC/5 category actually takes in a broad range of gun calibers and rates of fire, all with weapons systems of about the same weight (8 tons) and range (effective range = 540 meters). Weapon types range from medium caliber, 60 mm shells fired at 8 to 10 rounds per second, to large calibers-notably the Whirlwind 120 mm autocannon mounted on the MAD-3R Marauder. The Marauder's AC/5 fires at a painfully low rate of speed-only 3 to 4 individual rounds per second, but each 120 mm shell packs a tremendous punch. Like the AC/2, most AC/5s lose some accuracy at close ranges.

AC/10: The AC/10, such as the Luxor-D series carried by the CN9-A Centurion, is another intermediate class which includes both medium and heavy calibers. The Luxor-D fires 70 mm shells at 10 rounds per second, while the larger Kaliyama class 10 carried by the Kurita ON1-K Orion fires 90 mm shells at 5 rounds per second. The effective range is less than for an AC/5, but the larger number of shells fired with each cassette burst causes greater damage to the target.

AC/20: The monsters of the Autocannon weapon class, the AC/20, are generally carried only by assault 'Mechs. Each cassette round holds only four actual rounds, and these are cycled in extremely short, fast bursts which allow the cannon to run through 2 cassettes per second. The weapons are extremely heavy-as much as 14 tons-and their range is restricted by limits to the amount of propellant which can be packed into each shell cartridge. Maximum effective range for an AC/20 is only about 270 meters. However, those few, tightlyspaced, extremely heavy rounds cause terrible damage on impact, making them ideal weapons for such BattleMech monsters as the Cyclops and Atlas.

Space prohibits a detailed listing of all of the BattleMech autocannons by type, caliber, and rate of fire in this overview of weapons. As an overall weapons class, autocannons are highly regarded as an effective and efficient 'Mech weapon. AC/ 5s, in particular, combine long range with low heat build-up, and a solid punch balanced between the high-rate-of-fire/smallshells v.s. low-rate-of-fire/large-shells variables. These factors make the AC/5 one of the more popular BattleMech weapons, particularly if storage space aboard a given 'Mech allows storage for a full 20 reload cassettes. So popular is the AC/5, that its range and damage factors are often listed as standard autocannon data, particularly in older weapons listings.

As with other BattleMech weapons, all autocannon shells, whatever their caliber, carry for considerably larger distances than those listed as "effective range" in most manuals. As with other weapons systems, these figures reflect the difficulty in hitting targets as mobile as a BattleMech at ranges of more than half a kilometer.

BattleMech Weapons Crisis of Range and Accuracy

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