Re: the longbow argument (a good 'un). Check out Japanese history, specifically, the Onin War. There's a reason that the Tokugawa Shogunate banned muskets (teppo): Teppo allowed a warlord to drag peasents off fields, give 'em a few hours of firearms care and training, and fling them into battle en masse, where they could mow down the elite samurai with pure overwhelming numbers.
The crossbow is easier to use than the self-bow. The musket is easier to use than the crossbow. The easier a weapon is to use, the more people you can have using them. QED.
) That being said, The modern US army is not a Gunsmith any more than an IG guardsman is so if his weapon his heavily damaged, (Say by taking a round in the receiver casing!) he is not going to be able to fix it by swapping parts! He will need an armourer to repair something like that or if on the battlefield, just pick up his dead buddy's weapon! This is the same as for the IG trooper giving his weapon to an Artificer IMHO. I also agree with the poster who pointed out that a "standard" Lasgun (Particularly the ones from BC) is a very effective weapon against almost any other "Troop" level adversary. As to the Logistics: There is a scene in the game Mass effect 2 that very effectively explains this issue; When Shepherd rescues Tali she questions him as to why the quarians cannot go into full scale war with the Geth. (Given their success on this world.). Her own bodyguard explains to her that "What she has seen to date have been small unit actions that were relatively short in duration. In a full blown war supply lines get stretched thin and things get..messy"! This is one of the best reasons for issuing the Lasgun to basic infantry rather than anything else! Bear in mind that when the SM's deploy in an area they are normally acting in concert with a Strike cruiser (At least!) whose whole purpose is to support and supply the Astartes while they are "on mission". The Imperial navy basically just drops off IG regiments and then moves on to it's other mission requirements. Their resupply being up to the Munitorium to arrange (Often Imperfectly!) In extended campaigns or siege type scenarios this makes the Lasgun the ideal weapon as it never "truly" runs out of ammo! Your Unit will typically have enough Solar charging units (Or some equivalent) that you will be fully reloaded the day after the battle regardless of your supply condition! (Food might be a problem eventually but not ammo!
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