Without using Pattern shenanigans from Hammer of the Emperor, for which mileage may vary, if you're using splatbooks from previous Campaigns such as Rogue Trader, there's a lot of things you can do.
If I were a sniper, I'd settle for the Long-Las, simply because ammunition is plentiful and easy to acquire. In a pinch, if push comes to shove, you can throw a Laspack into a fire to recharge it.
A Long-Las, using Overload (+2 Dmg/Pen), a Whisper-Bolt Discharger (-1 Dmg, but functions as a Silencer and conceals the beam), and a Overcharge Pack (+1 Dmg), loaded with a Hot-Shot Charge Pack (Sets Pen to 4, adds Tearing, adds +1 Dmg, and reduces Clip Size to 1) would end up with the following profile:
Long Las, Basic; Range 150m; S/–/–.
Damage: 1d10+6E Pen 6; Clip 1; Reload (Full).
Accurate, Tearing, Felling (4), Silenced, Unreliable.
Throw a Telescopic Sight onto that, and you're good to go.
However, if I were the GM, I'd argue that several of these would be mutually exclusive. You're applying an Overcharge Pack to something that can already Overcharge, for example. It just doesn't make any sense to me. It's like they came up with the Variable setting rules (why is this not a special quality?) but then copy-pasted the upgrades and ammunitions from older supplements.
Hot-Shot Charge Packs can be used by Hot-Shot Laspistols and Lasguns, which are really just Hellpistols and Hellguns. It's dual terminology and very.. un-neat.
Anyway, there are, however, compelling arguments to be made in favour of the Sniper Rifle, should you accept upgrades from additional supplements. Notable, a Sniper Rifle would allow you to use a much wider range of ammunition (Bleeder Rounds, Manstopper Rounds, Blessed Ammunition, Barbed Rounds, Inferno Shells, Tox Rounds, etc), and many good upgrades:
Melee Attachment (Counts as Spear).
Maglev Impeller (Range +10, Dmg +1. Reload +1 Full).
Silencer (Silences, but without -1 Damage).
Fire Selector (Allows you to switch between three clips at beginning of turn).
Red-Dot Laser Sight (Who needs a Telescopic Sight with a range of 210m? +10 BS).
A Sniper Rifle with the above upgrades, using Manstopper Rounds, would have the following profile:
Sniper Rifle, Basic; Range 210m; S/–/–.
Damage: 1d10+5I Pen 6; Clip 20(x3); Reload (2 Full).
Accurate, Reliable, Silenced, Counts as Spear in Melee.
+10 Ballistic Skill.
One way to (ab)use the Fire Selector is to simply load it all up with the same ammunition, effectively tripling clip capacity. Arguably, it is still more useful to actually load it up with different kinds of ammunition, to preserve versatility, but that's up to preference.
If you have considerable room, I would take the Long-Las. It's easier to upgrade to reach this pinnacle, and you will never run out of ammunition. On the other hand, you will have to haul a metric ton of Clips around, and every single time you choose, there's going to be one full round you won't be able to do anything.
In anything remotely resembling close quarters, the Sniper Rifle would be preferable. With a potential effective clip size of 60, those 2 Full rounds of reloading will never come up, but you will also have to haul chargepacks around (for the Maglev Impeller). It also maintains that sweet Reliable Special Quality, and +10BS from the Red-Dot Laser Sight will help with the Accurate Special Quality, and with an effective Range of 210m, so, so, sooooo many shots should count as Short Range.Edit:
The prospect of using Barbed Rounds and then Bleeder Rounds against a single target in the distance, to then sit there and pick off his friends with Manstopper Rounds is.. classic sniper cruelty.
Edited by Fgdsfg, 26 September 2013 - 08:00 PM.