The XL4 is very similar to the Serious Sam 1XL2 Lasergun in looks and behavior. It fires two green lasers that are very close to each other. When the golden version of this gun is unlocked, the lasers expand to about twice their usual size, making them even more effective.
The XL4 is the ultimate rapid-fire weapon in the game. The projectiles fired by the weapon are bigger than the ones fired by the Tommy Gun, giving it more of a chance to hit an enemy, and it does more damage per shot than the Tommy Gun. It works well when combined with just about any weapon in the game.
Its high damage makes it very effective against every enemy type of enemy, but its real value comes from using it against enemies with high health, such as the Major Bio-mechanoid, and bosses. Its high damage per shot when combined with other high-damage weapons, like the LM32 Rocket Launcher, can quickly deal significant damage to high-health enemies. Multiple XL4s stacked together, along with other strong weapons, will decimate even the strongest enemies with ease.
Ammo for this weapon can only be found in the last chapter, making it difficult to use this weapon for an extended period in the other two chapters. Even in the final chapter, ammo can be somewhat scarce at times. However, Ammo Packs will give the player some ammo for it, letting them use it at least a few times when they run out of ammo in the first two chapters.