Why Lasgun suck Edit
IT'S NOT A LASER! IT'S A LITTLE LIGHT BULB THAT BLINKS! - Mr.Spock # 9001
The lasgun is rather pathetic compared to the mainline arms and armour of the rious Imperium, useful only by virtue of the fact that Xeno come in ridiculous numbers (Comparable to Bacteria) 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.
Most of the 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. They are on the same level of effiveness as throwing a rock as a Mobile Suit (Althrough to be fair, if the rock is throw at Leos, it might do some damage), 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, while an autogun magazine is usually 20-30 bullets (which, fun fact, is generally what typical lasguns set to max power usually can fire.) Plus you can recharge their batteries from any source, 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 on average not often not sufficient against anything besides clothes or a flak uniform's non-rigid bits,) 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 what amounts to the energy weapon equivalent of an especially snappy pomeranian.
Why Lasgun are being use Edit
Do we have anything better to use for the whole damn army. There is no omniversal god who can create Multiverse at will backing us up. So this is the best we could get.
---General Spock #69---