Lasgun
The humble (and we mean humble) Lasgun is the standard-issue armament of the average Imperial Guardsman in the Warhammer 40,000 setting. Given the incalculable number of Guardsmen under arms and the sheer scale of the Imperium itself, it is safe to say that the lasgun is probably the most common weapon in the entire galaxy that isn't some underhive piece of junk like stub guns, knives or other miscellaneous weapon. On the tabletop it shares the same rules with autoguns.
The name is rather obviously a portmanteau of "laser" and "gun", but argument rages over how the word is meant to be pronounced. Many claim that the "las" should be pronounced "layz" (or in other words say that it's pronounced with a long "a", as the first part of "laser"), but others contend that this sounds retarded, and "lazz-gun" (or a short "a" sound, as in "glass") is a better pronunciation. According to Games Workshop, its name is pronounced "Laze-gun"; however, Jeremy Vetock and Duncan Rhodes both say "Lazzguns," so it really is a toss up. (And unimportant).
It is almost universally described in the fluff as discharging with a sharp crack (caused by the beam ionizing the air it travels through), but some authors describe the lasround as either a "bolt" as in Star Wars or as a "beam" as in Dawn of War. Other features of the weapon have greater variation - some Black Library works and items such as the Imperial Infantryman's Uplifting Primer describe the weapon as possessing a fully automatic firing setting; this feature is represented by Rapid Fire rule on the tabletop, but not represented in Dark Heresy, which can be explained away by virtue of the fact that there are many different patterns of Lasgun produced throughout the Imperium.
There is also some dispute as to the color of the "beam". Some fluff claims it to be blue, while games like Dawn of War portray it as red or something of a reddish-yellow. The popular Gaunt's Ghosts series of novels by Dan Abnett say that the Imperial weapons fire blue "beams", while the Chaos weapons fire red ones. In order to fix this mess, we have proposed a Scientific fact on the issue...
- The Fact: the energy of each individual photon is determined by its frequency (i.e. colour); power output is energy per second, meaning the same power output is achievable with either more photons per second at a lower frequency (bright red) or fewer photons per second at a higher frequency (dim blue). In either case, the colour is also dependent on the gas it is traveling through, as the amount of energy transferred to the surrounding medium via [[1]] depends on the mass of each gas particle, while the brightness depends on the amount of gas particles, so the laser would look different on different planets. Regardless, a fired lasround would never look like a "bolt" to any camera (such as a human eye) operating at a frame rate lower than approximately a billion frames per second, so those depictions can safely be assumed to be heresy; it would look like any pulsed laser, i.e. a "beam".
Why the Lasgun sucks
See Also: Lasgun Patterns
IT'S NOT A LASER! IT'S A LITTLE LIGHT BULB THAT BLINKS! - Guardsman Woody.
"What do you call a Lasgun with a taclight mounted under the barrel? Twin-linked."
- Any 40k player evar (hilariously, GW has caught onto this. Less hilariously, on Regimental Standard they've got an in-universe nod where any Guardsman who makes this joke is sentenced to flogging).
The lasgun is rather pathetic compared to the mainline arms and armour of most of the other armies of the setting, useful only by virtue of the fact that Guardsmen come in ridiculous numbers (except in comparison to Tyranids, Chaos Cultists/Zombies, or Orks) and the application of statistical probability. The weapons are often derisively referred to as "flashlights," based on their individual uselessness, although this is arguably more of an example of how ridiculously tough everything else is in the setting.
The 6th Edition rulebook describes the lasgun as severing limbs at close range but further away it only goes about as deep as the liver, explosively flash-boiling said liver and all other squishy bits in the laser's path. That sounds awesome, until you remember that nearly every enemy of the Imperium has heat and energy-dissipating armor, redundant biology, or simply outrange them. Pretty much the only enemy an individual lasgun can reliably kill are other humans. They are on the same level of effectiveness as autoguns (which are basically AK-47s IN SPACE), except lasguns are even more durable, reliable, accurate (due to low to no recoil and the fact that the beam is not affected by gravity or wind, though shooting though a dust cloud or fog on the other hand is more problematic, so a B over all for atmospheric effects) and less dependent on massive ammo supplies; a single power-pack can, depending on the gun's setting, afford up to 100 to 140 shots on average, while an autogun magazine is usually 20-60 bullets (which, fun fact, is generally what typical lasguns set to max power usually can fire.) Plus you can recharge their batteries from Chimera generators, sunlight or even fire, while an autogun is useless once out of ammo for anything other than a fancy club or if you have the good fortune to have a bayonet, a vaguely sharp stick. Not that said bayonet on either weapon will help against orks or 'nids. And given the general competence of Munitorum depots, you'd probably end up with ration packs instead of ammunition, though this of course applies to lasgun power-packs, as well.
Combine this with most lasguns seeming to come pre-set to "medium power" (granting between 40 and 80 shots a pack with usually enough penetration power to reliably punch right trough Imperial Guard's flak armour (or xenos-made equivalents of such) and many places not bothering to actually include how to adjust power as part of basic training - probably (rightly) assuming the soldier won't live long enough for it to matter - and you end up with an energy-based assault rifle, that is actually good for taking down lightly-armoured infantry with resilience to ballistic damage roughly equal that of a normal human (as it is in case with eldars or tau), but that's exactly what it was designed for - nothing less, but also nothing more. Unluckly for typical guardsmen, however, there are warrior-creatures of the 41st millenium that are either equipped with armour, capable of deflecting even heavy stubber or bolter shells impacts, or biology so robust, that it is able to take a hit from heavy stubber's bullet in the chest and continue fighting on, or, in especially bad cases, warrior-creatures that have both of the aforementioned traits...
Why the Lasgun is still being used
Although better known as a "flashlight", some players also call it "The AK-47 of the 41st Millennium", albeit ironically. Instead of being reliable, tough, relatively inaccurate and having a tendency to show up in the hands of just about everyone, it's reliable, common as fuck (like 100 for every human in the galaxy common), pretty damned tough, and accurate but that is only by 40k standards. ...So, yeah, I guess it is the AK of the 41st Millennium.
The lasgun has very low recoil, especially in comparison to a bolter or even an autogun. More like a jolt than a kick, probably, due to sudden change in air pressure. The powerpack that the weapon uses can fire about a hundred shots before running empty and can be easily recharged through any standard Imperial power supply, direct sunlight, and even heat. A relatively common practice of Imperial Guard units cut off from supplies is to place their lasgun power packs in open fires, although this does lower the pack's lifespan considerably and is frowned upon.
The weapons are rather more useful in Dark Heresy than they are in the tabletop wargame, as their reliability, availability and plentiful ammunition become real considerations and they are rather more useful against the human foes that an agent of the Inquisition is likely to face.
Power packs for lasguns also vastly simplify a nightmare waiting to happen for ammunition logistics. Even if Autoguns were better in all ways than a lasgun, the Administratum would still use the lasgun for the power pack. Power packs, while not able to fit all sizes of lasgun apparently, can still be modified to fit, or be recharged in the middle of campaign. Especially important if you can't get any new supplies due to a variety of reasons (Enemy has orbital control, no one has your size caliber, ammunition expires, etc). This is important, since lasguns, the worst they can do if given the wrong size is not work. For an auto gun, with the wide range and variety of possible ammunition sizes, the best that will happen is that you won't fire your weapon, the worse, is that the shooter dies, and more importantly the weapon is destroyed. This is a strategy even being used today, to simplify ammunition supply problems by making all their guns fire the same cartridge. These same standards are impossible to enforce in the Imperium for an army the size of trillions.
One last thing about Lasguns is that they can be used as last-ditch grenades by basically making the entire power pack empty into the gun without ever actually firing it. It turns the Lasgun into an explosive comparable in power to a krak grenade or melta charge, depending on how badly it manages to fuck up whatever it was thrown at. It can even fuck the shit of a Chaos Dreadnought who thought he was going to make some Guardsmen go squish, and instead gets a lasgun-bomb surprise to the face. (It should be noted that this happened to a dreadnought whose front armor was already cracked from being hit by anti-armor weapons, so no way your overloading lasgun is going to help against an undamaged one)
One must wonder, considering how ass-cheap power-packs and the part of the lasgun this power dumps everything into to make it go "boom" are (compared to things like melta bombs and probably krak grenades as well,) why doesn't the Imperium make standard-issue grenades like that? Seriously, imagine guard squads with grenades almost comparable to melta charges ( which are pretty much miniature nukes,) and remember that squads can get multiple assault grenade launchers. The answer is probably that the Techpriests would go completely apeshit for desecrating holy technology and try to secede. Again. Unless there's some threat that forces them to make such weaponry or some red-robed asshat can convince enough other red-robed asshats that it was totally an STC design of course.
Five counter-arguments to the lasgun-power-pack-grenade come readily to mind, discounting most guardsmen not being aware of this particular tactic.
- Firstly, the power pack's detonation timing is highly unpredictable, and as we all know,
anything that endangers an imperial infantryman will absolutely not be consideredonly the most fanatical, stupid, or just plain reckless Guardsmen would be willing to use it regularly. - Secondly, while a lasgun is pretty inexpensive in comparison to, say, a bolter, its power-packs are not as cheap to produce (they make up for it by being so easily recharged.) And only veteran soldiers tend to carry more than a small handful of packs; packs which said veterans probably looted off other guardsmen who didn't get to be veterans.
- Thirdly, the blast yield from a power pack is never described as being particularly strong. In the aforementioned example the soldier managed to open a dreadnought's faceplate just enough for the local flora to kill it, which sounds commensurate to a glancing hit, estimating the explosion closer to that of a krak grenade (S6) or maybe a little stronger. While still powerful when compared to regular old frag grenades, this is nothing like the famous melta bomb.
- A weapon, no matter how shitty, is still a soldier's baby. A soldier without his main weapon is generally a dead man, commissar or no, and the only time you would be forced to use your own, custom, probably personalized rifle if you live long enough to know this tactic, is in case of true emergency or imminent death. The same case that the first case of this ever being recorded happened.
- Finally, in the instance where a Guardsman survives using his weapon and its magazine in such a reckless manner, he must then face the wrath of his superiors (If he survives the incident); the sheer number of Munitorum violations involved in using a lasgun and its ammo as a makeshift bomb are staggering (and while most alone would probably result in perfectly survivable corporal punishment, such as say being repeatedly rifle-stocked in the balls four dozen times while hanging upside down, all added up it's more pragmatic to just make the punishment execution to save some time.)
Unless he manages to secure a new weapon beforehand of course.
In all seriousness, the lasgun is very deadly when used in the hands of someone competent, and as being an effective combat weapon goes, anything not too heavily armored, like Traitor Cultists, Eldar Guardians, Ork Boyz, Tyranid Gaunts, and other Imperial Guard style forces are bound to be ridden with Laser holes. The Vostroyan Firstborn, for example, are renown for their precision with their lasguns and rewarded with high kill counts against everything from Orks to traitors. Elysian Drop Troopers are similarly known for exceptional marksmanship bred via necessity wherein they maximize lethality with minimal shots. And if you pray to the Emperor and get really lucky (given the Guard's numbers, they will get lucky, a lot), you might be able to take down a Chaos Space Marine (or equivalent) with it anyway - though Space Marines are also known to die after being poked (stabbed) by enough pointy (sharp hard) sticks on occasion after all or being stomped on by enough human beings at once Also, a point- or near-point-blank shot at maximum power from a lasgun can penetrate a Space Marine's helmet and turn his brains into impromptu house paint.
It should be noted that the lasgun is stated to be able to destroy a slab of cement, which a .50 cal anti armour rifle would be able to do today. Although that could because the Lasgun is placed on a slightly higher setting or it may be a different pattern of Lasgun.
A quote from Black Crusade (RPG) sums up the las gun perfectly: "The Legionnaire that scoffs at a lasgun has not charged across an open field against a hundred of them." Of course, in Black Crusade a Legionnaire in power armor is all but impossible to wound with a lasgun (and that is what Horde rules are for!).
Uses for the Lasgun
- Warming soup
- Cigarette lighter
- Changing TV channels
- Selling to buy a new weapon
- Pissing off Thunderhawk pilots
- Shining in enemies' eyes
- Throwing at people (may cause more damage than shooting it at them)
- Burning ants
- Paperweight
- Laser sight for a boltgun
- Aide during PotentiaPunctum presentations
- Light shows
- Laser tag for kids (who are probably more dangerous than the gun itself)
- Magic shows for kids
- Lighting candles on birthday cakes
- A Laser pointer
- Entertainment for your space-kitties
- Shooting bottles
- Hitting your officer's pipe (Warning, will result in BLAMing)
- Flashlight
- Substitue baseball bat
- Salvaged for actual useful stuff
- Horsie rides
- Chair
- Creating a makeshift rave
Other laser weapons
The lasgun also comes in carbine, pistol, bullpup, sniper ("long-las"), and light machine gun (the heavy lasgun, which so far seems to only exist in Black Library) - (Heavy laser is just a crew-fired multi laser) varieties, and the Imperium fields many other weapons based on the same technology, such as the hellgun (a powerful lasgun powered by a backpack power pack), the mighty lascannon (mighty being relative... SPESS MEHREENS can equip it), the even bigger volcano cannon and turbo-laser, the even bigger Defense Laser, and the bigger still laser weapons mounted on starships. Must be a different type, though, because a broadside from a Retribution class battleship can devastate half a continent depending on the calcs. A single barrage from an Imperator class Titan can devastate an entire city with weapons as strong as modern day nukes. Keep in mind how large an Imperial city is.
Oh, and multilasers.
Laspistol
See main page, Laspistol
Lasgun
You know'em, you love'em. There really isn't a point in repeating what has already been said since you are on a page talking about this wonderful piece of Imperial equipment other then putting it in the Lasgun family. Of course there are certain modifications that may breach the line on what may count as a Lasgun. But overall, it is cheap, effective and put a lovely little dent to most light infantry contrary to popular belief.
Just don't try and attempt go all Leeroy Jenkins on this thing. The Lasgun is a light assault weapon, not a Titan-busting Volcano Cannon.
| Edition | Range | Type | S | AP | Damage | Abilities |
|---|---|---|---|---|---|---|
| 7th | 24" | Rapid Fire | 3 | - | N/A | - |
| 8th | 24" | Rapid Fire 1 | 3 | 0 | 1 | - |
Hotshot Laspistol
See main page, Hellpistol
The Hotshot Lasgun's little brother, also known as Hellpistol (although there do remain some canon conflict about these two weapons designation). Hotshot Laspistols are typically hand-crafted, rather than mass-produced in factories, and most are hundreds of years old and have acquired histories over the course of centuries of use in combat. Unless otherwise specified, a Hotshot Laspistol remains the property of the Departmento Munitorum, though an individual can be awarded one for heroic deeds. A Hotshot Laspistol fires a higher-intensity shot than a laspistol, cauterizing just about any wound it causes and preventing blood from being shed. For this reason, Hotshot Laspistol have been sanctioned for use as execution weapons for officers and commissars, as a shot to the condemned soldier's head will prevent any blood from staining their uniform.
Hotshot Lasgun
See main page, Hellgun
A variant of the Lasgun, also known as the Hellgun (although there do remain some canon conflict about these two weapons designation), the Hotshot Lasgun and Hotshot Laspistol are weapons used primarily by the Stormtroopers (and presumably other arms of the Imperial war machine). These are juiced-up versions of the Lasgun charge pack inside a normal Lasgun. They are designed to be used by elite troops or officers, who are generally better shots. Instead of the Hellgun's tactic of using lots of batteries to shoot several times per second, Hotshots use a super-concentrated laser blast to achieve the same kind of armor-penetrating power.
| Edition | Range | Type | S | AP | Damage | Abilities |
|---|---|---|---|---|---|---|
| 7th | 18" | Rapid Fire | 3 | 3 | N/A | - |
| 8th | 18" | Rapid Fire 1 | 3 | -2 | 1 | - |
Hotshot Volley Gun
Another variation of the Hotshot category of Lasguns. These weapons are borne into battle by Tempestus Scions to deal with armored enemy infantry. The Hot-Shot Volley Gun is a larger version of the Hot-Shot Lasgun that "incorporates penitent-class heat sink arrays" which means that they "can maintain a punishing rate of high powered fire".
Think of them as a fully automatic LMG version of the regular old Hotshot Lasgun. As you can imagine, the sheer amount of Dakka means that they are more likely to be situated within the heavy weapons category then the normal Hotshot Lasguns. They are known to fire with a distinctive spitting howl.
Mining Laser
Mining Laser is not formally a weapon, but a tool for breaching tunnels in the mining process. In some cases though the Mining Laser can be used as a weapon, often by Genestealer Cults. For example, Dvarlock pattern Mining Laser, founded and identified by Tempestor Gulack of the Kappic Eagles have been modified so it can blast the hole through a meters-thick bulkhead with a single pull of a trigger. It also features three hand-grips. indicating its use in combination with a tertia pattern servo-arm.
There is also the Heavy Mining Laser which is a heavier variant of the standard version, used on Goliath Rockgrinders. Although to be honest, it is only 'heavy' because it is on a turreted mount, other than that there is very little difference between the Heavy Mining Laser and the regular old Mining Laser.
Long-Las
In the good old days the Imperial sniper rifle was the poorly named 'needle rifle' which was in fact a kind of laser weapon. Well, partly. It had two parts to each shot. It fired a narrow beam laser to burn through armor, and then it fired a 'needle' bullet; a spike of some kind of metal filled with horribly poisonous toxins. With the armor removed first, the spiky bit all but ensured a kill if you hit, spurting deadly death juice into your unfortunate body. Sadly they weren't especially well conceived weapons (hitting the same spot with two different weapons, one that responds to wind and gravity, and the other that doesn't is something of a challenge) so they've pretty much been written out of the setting these days. Now the term "sniper rifle" is used fairly loosely in the Imperium; many sniper rifles are simply over-powered lasguns called long-las rifles, while many others (such as those used by Space Marine Scouts) are high-velocity slug-throwers which have more in common with autoguns than they do with energy weapons. Then there are other more exotic variants firing poisoned darts or even stranger payloads. All of these variants have pretty much the same effect on the target, unless you play older editions or use special characters who have rules that say otherwise. Or play Dark Heresy.
However, since you are on the Long-Las category, we might as well talk about it. The Long-Las is a sniper variation of the Lasgun with a much longer barrel for increased range and accuracy, and also to prevent overheating. However the barrel makes a Long-Las up to twice as long as a standard Lasgun and thus difficult to use in close quarters.
Within the Imperial Guard the Long-Las, formerly known as the Sniper Variant Lasgun, is issued only to those Guardsmen with the necessary marksmanship skills and knowledge in stealth and scouting operations. It uses the XC 52/3 strengthened barrel, longer and thinner than normal models, and lacks a charge setting slider, instead using hotshot power packs. It's also much quieter than other lasguns and features a flash suppressor to dampen the revealing flashes of its shots. However the increased wear on the barrel from using the overpowered energy packs means more frequent barrel changes than is usually required for normal lasguns.
Lascarbine
During the Great Crusade the Lascarbine was the great grandfather of the Lasgun. Basically the same weapon as the Lasgun in a smaller package. They were standard issue among the Imperial Army and Solar Auxilla. In modern WH40k, a Lascarbine is designed for use by special operations units and is usually employed by Drop Troopers or scout units of the Imperial Guard such as the Elysian Drop Troops.
Auxilia Lasrifle
Auxilia lasrifles have better range compared to their inferior knockoffs. These have the option of taking Blast chargers. A one time ability that does more damage for skipping a turn. Roles of 1 prevent the player from using them for the remainder of the game. They also come standard with Collimators. Switching out Rapid Fire for Heavy 2. Making any opponent think twice about about charging a squad of Solar Auxilia. As if a Super Heavy tank as a Dedicated Transport wasn't enough reason to stay out of range.
Blast Pistol
Not to be confused with the Phosphor Blast Pistol, another 30k era weapon that fires completely different rounds.
Basically a supped up las-pistol that explodes in the user's hand. Their description makes them seem like laser revolvers used by officers of the Solar Auxilla. To mirror when an officer during the 19th century was issued a sidearm. Giving him a better gun than the line troops who had to use leaver and bolt actions. Which isn't the case here.
These bespoke weapons like the Hotshot Laspistol and Hellpistol were able to fire only a handful of shots before reloading, but their damage output rivals that of arcane Volkite Weaponry. Due to this, Blast Pistols were seen as an emblem of wealth and prestige, and many were works of art in their own right, and thus they also became a widely used form of decoration and reward for extreme gallantry and commendation within the Solar Auxilia regiments.
On the table top. Blast Pistols are S5 Las-pistols with Twin Linked and Gets-Hot. Archaeotech and Plasma pistols are more useful then these things.
Digital Lasers/Digital Weapons
These are actually melee weapons. However there isn't really anywhere else to put them. In 40k they are exclusively made by Jokaero. During the Great Crusade and Horus Heresy they are weapons of unknown Xenos origin. This section describes how the Imperium at large uses them.
Digital weapons are best described as a small laser used by Space Marine officers. It allows them to re-roll one failed hit during the Assault/Fight Phase. Which is decent, However it isn't anywhere near as cool when their used in Black Library books or the weapons stated to be used by the Jokareo. Only the Xenos monkies have them on the table top until the actual 8th edition Codexes are released.
30k Digital Lasers are as usual better than the 40k version. Rather than just Space Marines, Inquisitors and the occasional gun/chain/power sword toting hero. Every officer had access to them. They are short ranged but deadly weapons that are "small enough to be concealed in a ring, gauntlet, sword hilt or helm." So they should be as strong as a single Hot Shot Lasgun, Lasrifle or Las-Lock beam.
In the Horus Heresy game a Digital Laser gives the model one additional attack. So the officer doesn't have to give up their sole ranged weapon for an extra melee hit. One would assume either weapon would also allow an extra ranged attack with the same strength and AP as a Hot-Shot Lasgun or Archaeotech Pistol. Like how the Servo Harness gives Techmarines extra ranged and melee weapons. However Games Workshop and Forge World aren't nice enough to give players an option that would be useful in more than one situation. Without making them pay extra real life money for it first.
Las-Lock
Like everything like in else in Warhammer 40k. Whatever the forces of the Imperium of Man have, the Adeptus Mechanicus will have discovered or created a better version of it. That they don't bother sharing with their own allies. As with every other fraction in the game. Tech Thrall's are thus far the only know Ad-mech troops to carry las-weapons. Admech Las-lock's sacrifice rate of fire for more damage per shot. Making it a superior version of the Hot-Shot lasgun.
Mitralock
There is also the Mitralock, a laser shotgun with reduced range. Both have the option to upgrade to Induction chargers increasing their shots to two.(represented as Assault 2 in game.) While still allowing them to Assault with no penalty. This turns them into a high risk unit to for any opponent dumb enough to charge them.
In terms of tabletop, the Mitralock is the Scattergun of the Las Family. It is an 8" range Las-lock, but it gains Shred. It also has Induction Chargers which is an optional attachment to both Las-locks AND Mitra-locks (HH3, p. 221) it upgrades them to Assault 2.
Lascutter
Lascutters are a powerful but extremely unwieldy type of Laser Weapon. Originally industrial tools used for cutting through armored bulkheads and dense ores, these weapons make use of disruption field-assisted short range laser arcs. They were later utilized for warfare, being used in sieges where they were able to breach enemy fortifications and if necessary become devastating close-quarters weapons. On the table top. These thing suck. Only Breachers can take them. The Cumbersome rule reduces the model's WS1 and can only make a single attack. Take Graviton guns instead.
Lightning Gun
Despite the name, Lightning Guns are a type of laser weapons used by the AdMech. Whilst they do use electromagnetism, most of the killing power is from the pew pew lasers. Lightning Guns are Great Crusade era weapons used by various Adeptus Mechanicus troops, most notably Thallax.
This aptly named weapon takes the form of a baroquely designed carbine connected to a micro-reactor or power core. It fires an ionizing las-beam along with a powerful phased discharge of electromagnetic particles. The ensuing effect makes the weapon able to overload mechanical targets in addition to its effectiveness against organic enemies.
Multilasers
See main page, Multilasers
Lascannon
See main page, Lascannon
Superheavy Laser Weapons
See main page, Superheavy Laser Weapons
Properties of a lasgun
It's easy to imagine being hit with a lasgun would be like having a hole burned into you like an ant being burned by a magnifying glass. That, of course, is not nearly grimdark enough to be the truth.
A military DEW (or Directed Energy Weapon since military forces love TLAs (Three-Letter Acronyms)) comes in several different types, from microwave weapons which are mostly used to short out electronics, to Electrolasers which use lasers to ionize the air into a semi-superconductive channel, allowing an electrical current to be projected between two points like a glorified (albeit high-power) taser. This may in fact is likely how necron Tesla weapons work but that is neither here nor now. A lasgun however is most likely to be a pulsed energy laser. A pulsed laser works by imparting so much energy to an area so fast, that it turns into plasma and explodes. Modern versions create a pressure wave strong enough to stun and knock a person out (termed "Pulsed Energy Projectile), but they are less then-lethal weapons that don't penetrate things very well by design, while the lasgun is not.
Being hit with a lasgun would (could) look and feel more like you were hit by a concussion grenade held up to your chest. You would see a bright flash of light as your skin or clothing vaporized into plasma, much like a high-end camera flash going next to the wound. Higher-power laser weapons might cause enough of an explosion to blow you back and maybe knock you unconscious, or if you got hit by one of the Lasgun's anti-tank big brothers, vaporize you outright turning you into an impromptu plasma grenade for the rest of your squad to deal with. The explosion would create enough hydrostatic pressure to likely scramble your internal organs and maybe snapping your bones in parts of your body distant from the explosion. However, if the lasgun hit something like armor, or even clothing it might induce an explosion only on the surface of the armor leaving the rest of you safe, though most assuredly stunned and dazzled from the plasma explosion. This explains why the Lasgun has a AP of only -. A Bolter's bolts, on the other hand, penetrate the exterior and then explode inside the target, meaning it can deal with armor and tough alien targets like Orks much easier, since you're effectively ignoring the armor on anything the mass-reactive warhead can punch through. The lasgun is clearly nothing to sneeze at; it's just that the vast majority of the Imperium's more exotic enemies are capable of taking that kind of punishment most of the time and still keep on fighting.
However, all that is based on the previously mentioned less than lethal lasers, which are specifically designed that way on purpose. A laser can easily be designed to maximize impact or penetration, and autogun bullets, which could likely go right through many parts of you, also have AP - anyway. A theory more in line with the stated effects of a lasgun shot is that it would use multiple insanely rapid micro pulses to BORE THROUGH light infantry-grade armour, clothes and flesh to reach internal organs. Imagine getting drilled into by hundreds of tiny explosions, all within the span of milliseconds. This would leave wound very similar to the ones described in the Uplifting Primer, nasty burnt holes.
While the lasgun is portrayed in some media as having recoil, it doesn't in any true sense of the term. There might be a slight jerk on the barrel from the air pressure differential created by melting a hole through the air, a la a thunderclap, but the effects would be much more pronounced on the target (since there's no direct exchange of kinetic energy, the recoil can be zero, while there is a noticeable impact.) It might make a loud "crack" noise, due to Compton scattering, if it is fired in atmosphere and an abundant source of electrons is available (such as from the gun itself, if it is design appropriately). It should also be noted that at long range, if you were shot with one, there would be a substantial delay between the shot hitting you and you actually hearing the noise, making it an effective sniper's weapon. The second most common counterargument to this is that you would be able to follow the beam back to the sniper, but remember: you don't see the beam. It's too bright for you to be able to see it clearly, and you're going to be flashblinded by both the plasma explosion and the laser itself, if it's in a visible spectrum. Which it doesn't have to be. In fact, since Imperial lasgun is described as firing blue or white beams, the laser itself is likely ultraviolet, meaning there would be some brightness as it carved through the air, but not as much as a high-power laser backscattering into your eyes and giving you an impromptu round of Lasik.
Coming to that, the continued use of a lasgun is probably going to render you blind. Remember, this is a gun that shoots a whole bunch of light to do damage. It's going to be even harder on your retinas, even if you're not the one being hit by it. After all, just because you can't see UV light doesn't mean it's not bouncing around your eyeballs-this is why UV protection in sunglasses is such a big deal, and why your eyes sometimes hurt when you step outside on an overcast day. There's still light there, and it's still fucking with your very easily damaged optics. So unless the Departmento Munitorum issues some kind of protective eyewear or contacts to the Guardsmen (and don't kid yourself, this is 40K. They don't.), their vision is going to get worse and worse over time, until they finally go blind. Fortunately, this would take about six months to a year of exposure of combat level conditions, or one apocalypse battle on a gunline, and most Guardsmen are not going to live that long on the battlefields of the 41st Millennium, and if do live that like then you're an elite soldier (or commissar/commander) worth the laser eye surgery to keep fighting since you're now worth many times what a normal guardsmen is. Or you manage to buy a cheap pair of shades at your troop ship's market, which are actually pretty common even then.
Except that you don't have to worry about laser back scatter or (to a lesser extent) lasers sucking at range. Lasers of sufficient power don't reflect. As in at all. Their light and energy is basically absorbed on impact. So the only light you'd have to worry about is the plasma flash of the impact and beam (if present). Also, lasers that can blast holes in to you may suffer from dust or distortion effects, but non-vacuum frequency lasers will get through air well enough simply on the basis that air is much much less dense than what it is intended to actually bore through. Also adaptive optics can at least partially mitigate said effect. As far as inverse square law goes, lasers are COHESIVE beams, and can easily be focused and stay focused well within firing range, even for typical sniper ranges, if aperture is large enough and/or wavelength is short enough to counter diffraction(UV is very short).
TL, DR: People disagree but it's not fun.
Too short, want more? Go here.
Why the Lasgun doesn't suck (an alternate take)
The purpose of the primary infantry weapon is not to take out everything that the infantryman might face. It's to provide volume of fire and self defense from other infantry. As today the average infantry man is equipped with an assault rifle that is not capable to pierce trough light armor up, nor is intended to. That's why in infantry squads you have infantry support weapons, like machine guns, mortars, rocket launchers, grenade launchers, anti materiel rifles etc. An infantry squad is supposed to take on hard targets with its support weapons where light armed troopers provide cover and logistic support. Also they are supposed to call in heavy support from artillery/air/tanks etc.
The astra militarum is fully equipped to handle harder targets with a variety of powerful infantry support weapons (plasma rifles, missile launchers etc) and a huge selection of heavy fire support from lascannons to leman russes.
In this context the lasgun is a fantastic weapon. Far superior of the today assault rifle even considering the battlefield differences. The lasgun is extremely rugged and reliable. Will require almost zero training becase has no moving part and no recoil. The "no recoil" part being extremely important, because it means that untrained troops will still be able to put down relatively accurate full auto fire, a practical impossibility with today guns. Lasgun fire will rape non armored or lightly armored infantry and still pose a threat to medium armored infantry. And will absolutely destroy unarmored vehicles. A bullet can cause virtually no damage to a truck, but a lasgun bolt will cripple it.
The logistical ability of giving hundreds of shots to every single infantry man, in the form of compact, standard and rechargeable power packs is the ultimate dream of every army. The level of flexibility that this allows is incredible and is unmatched by virtually any other infantry weapon in the 40k universe. And remember "amateurs talk about tactics, professionals talk about logistcs".
The lasgun is so an incredibly flexible weapon that it could be even modified into firing more powerful shots, still retaining part compatibility and power source (therefore logistical chain). So it's well suited for the lowly grunt and the special forces operatives, that will also be able to use it's superior training and physical fitness to carry literally THOUSANDS of shots worth of power packs. This will enable all sort of long range military operations deep in enemy territory and far from supply lines that we can't even think of today.
And yes, in 40k everyone and their mom has at the very least carapace-grade armor that will offer a decent grade of protection from lasgun shots (and that's not counting the fact that even carapace armour could be rather reliably pierced by lasgun's beams, abeit this would generally require a guardsman to close to about 100 meters distance to his target as opposed to lasgun's 400-500 meters effective range against infantry, donning only light flak vests and regular steel helmets). But that's not a weakness of the whole lasgun concept. Far from it. It's the ultimate victory of it, because it means that your enemy has to spend a shitload of money to put every one of his soldiers in expensive top grade armor just to have any hope not them to be instantly destroyed by your endless stream of dead accurate full auto lasgun fire.
Las weapons and AA
The problem of hitting a flying object with a gun is that the flyer is moving at high speed in a three dimensional space. That means that to hit it with a "bullet" you need to know where the flyer be when the bullet will cover the relative distance between the shooter and the target. You need to detect the precise three dimensional position and velocity vectors. Then you have to factor the variable speed of the bullet and his ballistic trajectory. And even if you do all that with the near-perfect accuracy, the target might just change his velocity (maneuver) and dodge it.
That's why in modern warfare all AA, except at the very most close range, is handled to missiles instead of guns.
All this problems disappears if you have a practical las weapon that will fire a las beam at speed of light. Even if your target is - say - 300 kilometers away, the las beam will reach it in a millisecond. Flying at mach 3, the object would displace by only one meter in one millisecond and still be hit. This mean that hitting a flyer with a las weapon would be extremely easy even without any dedicated equipement if close enough to be seen by naked eye. With radar auspex firing control you will basically hit flyers as soon as you detect it. The main strength of flyers (being harder to hit) will disappear and they will become the easier targets on the battlefield because they have no chance of cover and they cannot be as hard armored as something on the ground.
That's it, practical las weapons will probably make all "airplane" like stuff disappear from battlefield.