M53 SLAMr

The M53 Shoulder-Launched Artillery Missile launcher, and commonly known as the "Long Tom" or the SLMR (pronounced "slammer"), is a is a shoulder-fired heavy weapon issued to personnel of the UNSC Marine Corps during the Insurrection and Human-Covenant War.

History
In 2480, the UNSC opened a contracting bid for their next generation of shoulder-launched rocket launchers to replace the older M30 Striker systems. The UNSC’s criteria stipulated that this new rocket launcher had to be able to target both land and air vehicles, capable of locking onto targets, man portable, and reusable.

Several major corporations pitched in; Chalybs Defense Solutions, Acheron Security, Misriah Armory, Shinoda Heavy Industries, and many others sought to secure the lucrative contract. One of these was Köning Arms, a small manufacturing company based on New Carthage that entered the bid with what was then-designated the LT-1. When they entered the ring, few thought much of their bid. At the outset, it appeared that Köning was the underdog in the competition, going up against more established rivals and titans of industry. However its design passed through several rounds of selection trials until it made it all the way to the finals. Eventually the competition was narrowed down to two designs; Köning Arms’s LT-1 or Misriah Armory’s XM41.

During the final evaluation tests, the LT-1 seemingly had the edge over its competitor. It had a longer range than the SPNKr, it carried more ammunition, and it packed a bigger punch. But to Köning's surprise and chagrin, the UNSC gave the contract to Misriah Armory instead, citing that the LT-1 was too heavy and cumbersome to be carried around the battlefield by foot soldiers and was better suited for targeting aircraft than surface targets. In fact, many test refrained from firing it from the shoulder in favor of steadying it against the ground.

Disappointed, the design team went back to the drawing board. But rather than scrap the concept, they accepted the feedback and decided to make the bug a feature. They reworked the design into a man-portable artillery system, able to target ground and air vehicles as well as provide in-direct fire support.

Design
The M53 is a heavy tube with a revolving magazine that carries five rockets. The magazine can be swung out and reloaded individually, or replaced wholesale with a fresh cylinder with rockets.