The Lasgun, also sometimes referred to as a Lasrifle, is a directed-energy antipersonnel weapon used by the military forces of the Alliance of Nations (Notably the Imperium of Man and United Kingdoms of Water), and it is the most common and widely used type of laser weapon in the galaxy alongside the DC-15A blaster rifle. Lasguns are reliable, easy to maintain and to produce, and are readily available on Imperial regions. A Lasgun has a longer range than a Laspistol, but is nowhere near as powerful as a Lascannon nor does it possess the rapid-firing qualities of the Multi-laser or the Hellgun. Though not as powerful as kinetic projectile weapons such as the ubiquitous Bolter, the lower cost of production, the lack of a requirement for ammunition production and resupply make the Lasgun the best choice for the large forces of the Imperial Guard. The Lasgun uses a small portable capacitor power pack to produce a focused pinpoint laser beam which is strong enough to take an ordinary human arm off with one shot but is not as effective against the more durable alien bodies and stronger types of personal armour.

A Lasgun's beam also cauterizes the wounds it inflicts due to the immense heat given off by the shot. The Lasgun is effective when used en masse, but considerably less effective when used alone.

The Lasgun uses the same basic technology and operates along the same lines as other laser weapons, emitting a beam of highly-energetic, focused, coherent photons. The high amount of energy carried by the photons of the beam causes the immediate surface area of a target to be vaporized in a small explosion. It is a relatively unimpressive weapon when compared to many of the other high-technology weapons of the available in the galaxy, but it is capable of cleanly severing limbs and potentially even piercing the Power Armour of a Space Marine (but usually only through a vulnerable spot in the armour). Most Lasgun designs have iron sights mounted along the top of the weapon. It is powered by a small rechargeable power pack located beneath the weapon and in front of the trigger guard which can be recharged in a number of ways, including by sunlight. These power packs can also be "overcharged", a trick used by Imperial Guard veterans, which causes the pack to explode, turning the weapon into a makeshift grenade. This tactic is only used in last-ditch situations as it results in destruction of the weapon. Lasguns have numerous power settings for adjusting the power of each shot and to conserve power (resulting in a weaker laser shot fired). The weapon can be overpowered with a "Hotshot" laser capacitor pack, providing more powerful but fewer shots. The Lasgun mounts a bayonet lug, allowing the weapon to be fitted with bayonets or combat knives.

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