This is mostly a sci-fi error in the fluff, but why would a long-las need a longer barrel? Energy weapons have no need for rifling like a projectile does. The only reason I can think of is to house stronger emitters in order to boost the power of the laser, as this is the only thing that will make a laser more useful at long range.
This is in an atmosphere of course. In vacuum, all lasers have infinite range and accuracy.
This was semi-answered in one of the Gaunt's Ghosts books, but it had mainly to do with 'hot-las' employed by their chief sniper, Larkin. He said something along the lines that longer las barrels are more reinforced than regular ones, which help to maintain the power of the las; the las power in a sniper packs more punch than a regular las, and of course it shoots at a longer distance. Also las barrels in sniper guns have to be replaced regularly, so if the normal sized barrels are used, then that would be a waste of material. Better to build efficient longer las barrels than waste regular ones that are employed by the rest of the troops.--Vindicta 18:30, 8 January 2009 (CET)
What about the Tau Rail Rifles? Why aren't those included in the list of sniper rifles? I mean, sniper drone teams; which use rail rifles, have the word in it "Sniper".Aryeonos 01:00, 24 November 2010 (UTC)