The Lasgun is the most common weapon in the Imperium's weapon arsenal. It is cheap, effective and mass producable, as such it has become the standard issue weapon for all Imperial Guardsmen.
The weapon works just like all laser weapons. The gun fires a shot of highly dense photons (light 'particles') at a target. Upon impact the photons create a miniature explosion vaporizing or severely burning any nearby matter.
Lasguns also offer levels of custom ability. They can be assembled into sniper rifles, given bayonets or augmented with additional projectiles. Though not as powerful as kinetic projectile weapons, 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. The sniper variant of the Lasgun, known as the Long-Las, is the preferred weapon of the Imperial Guard's sharpshooters. The barrel of the Long-Las is extended to bolster the weapon's accuracy. The barrel requires replacement after every 20-50 shots depending on the power setting and cooldown time. For this reason, the Long-Las is outfitted with a "slide-lock" barrel, which is easily locked and unlocked from the weapon's housing.
The standard Lasgun pattern used by the Imperial Guard is known as the M35 "M-Galaxy" Pattern, first put into use in 2546.789.M35, although thousands of variant models, marks and patterns exist. The Cadian Shock Troops, for example, commonly bear the M36 Kantrael Pattern Lasrifle, originally manufactured on Kantrael as the name suggests, which is a weapon known for its sheer robustness.The Catachan Jungle Fighters prefer the Mark 4 Lascarbine, which has less cowling than the M36 and is therefore lighter and easier to carry in the dense jungle environs preferred by the Catachan regiments. Other common marks include the easily manufactured Mars and Armageddon Pattern Lasguns, the much sought-after variable power setting Triplex Pattern and the short-barelled, folding-stock models used by Imperial Guard mechanised infantry, tank crews and troops assigned to starship or space station details. Even more exotic are the intricately crafted heirloom weapons used by the troops of regiments of the Vostroyan Firstborn and the Accatran Pattern Mark IV, which is much valued by Elysian Drop Troops and other drop troopers for its compact size and accuracy at short range. Despite these variations, the main mechanism of every Lasgun remains the same in almost all regiments. This makes the logistics of supplying multi-regiment armies a much simpler matter for the Departmento Munitorum. Other variants of this weapon include the more compact Laspistol, the anti-armour Lascannon and the more powerful and expensive Hellgun. The Imperial standard Lasgun, as used by most of the regiments of the Imperial Guard, has many attachments including (but not limited to) several types of scope, bayonet, laser sight and flashlight.
The Lasgun and Laspistol are possibly the weakest weapons in terms of pure killing power of all the weapons in common usage by the Imperial military forces, and are widely and scornfully known by Imperial Guardsmen as "flashlights." However the true power of Lasguns resides in their massed, concentrated use. It has also been demonstrated that even a Laspistol beam is fully capable of killing an unarmoured target, slicing limbs off and, if fired into a target's eye, searing the brain and causing immediate death.