Metal Eater

The Metal Eater (鋼鉄破り(メタルイーター)) is the nickname given to a series of powerful sniper rifles used in the Toaru Majutsu no Index universe. The most famous of course is the Metal Eater MX, one of the standard weapons that are used by the Sisters along with the Toy Soldier.

Metal Eater MX
The Metal Eater MX (メタルイーターMX) is actually a Barret M82A1 anti-tank rifle. In the Toaru Majutsu no Index universe it has the reputation of blowing up a tank from 2000 meters away during the Gulf War. The Barret M82A1 that are used by the Sisters however are prototype models that allows the use of the full-auto feature, allowing for rapid fire usage. The feature was originally removed for the mass production as the recoil was excessively powerful, which can smash a shoddy helmet into pieces.

The Sisters who use the rifle have no problem with it as they have received the necessary information using Testament on how to counteract and ward off the powerful recoil. The rifle had a length of 180 centimeters, uses .50 caliber anti-tank bullets, and can fire it at speeds of 3070 kilometers per hour.

Metal Eater M5
The Metal Eater M5 (メタルイーターM5) is an anti-tank automatic rifle that was used by Academy City in World War III. It was originally the MX, only with modifications done to the handle and scope, and a water cooler was installed to it. It is capable of causing some damage to a Powered Suit. It still retains the massive recoil that was present in the Metal Eater MX.

Sisters Arc
A Sister uses the rifle in full automatic against Accelerator as part of the Level 6 Shift Project. Needless to say it is ineffective against Accelerator's Redirection, utterly destroying the rifle and injuring the clone severely.

Freshmen Arc
Hamazura Shiage and Hanzou comes upon coin lockers that contain weapons, one of which is the Metal Eater M5. Shiage later uses the Metal Eater M5 against a Powered Suit that is charging him and gets a taste of the powerful recoil it has. Later, he uses its incredible recoil to avoid being hit by the Gatling Railgun fire of the FIVE_Over Modelcase_"RAILGUN", and later abandons it to escape.

Side stories
Sunazara Chimitsu is hired by the Academy City Board of Directors to destroy an overpass that leads to School District 3, where a conference between them and other leaders of state was being held. This is because a satellite guidance vehicle containing gallons of the noxious rocket fuel hydrazine has been hijacked by the terrorist, and the driver is forced to comply lest he will take control. Chimitsu uses a Metal Eater to destroy the overpass, and completes his mission.