Cpt. Harkonnen said:
Ok, 1st off.. a .50 sniper rifle is WAY too complex of a gun for the 41st Millennium. This is 40k where even the most basic of things we take for granted here in the now is considered Arechotech. Furthermore, this game is about flavor, not substance like stats and min/max. Kills me to see so many people concerned with game stats than with the flavor or spirit of the game. Most weapons in Rogue Trader all do the same amount of damage with a +/- a few points. Rogue Trader is kind of like Star Wars in the fact that its Space Opera more than it is Sci-fi.
Serve the Emporer today, you may be dead tomorrow…
In a setting where caseless ammo gun that can easily swap between magazines (something that is hard to do today even), with all kinds of exotic ammo. They have laserguns, powered armor, giant mecha, starships, FTL, amazing efficiency and so much more.
Archeotech is simply put, AMAZING, it is efficient, durable and powerful. It outstrips our modern tech overall, the only area where modern day humans have better tech would be in computers, and in the 40k setting they outstripped us there too, even getting fully sentient. So they regressed in that area because of the risk of robotic uprisings and chaos infesting and corrupting their tech.
Besides, they have heavy stubbers (possibly around .50 cal) and autocannons (repeating powerful cannons that fire explosive ammo)
If a player wants a .50 Cal Sniper Rifle (for this example, let's take a heavy stubber, make it S/-/- and accurate with an appropiate sized magazine), what is the issue, it won't even be as good as the Angelus Bolt Carbine and the Sniper Bolter (both of which have great damage, more pen and tearing WITH accurate), so it hits weaker, will be big and heavy, obvious to see (but will have cheaper ammo). So why does it matter? It won't be a game breaker, just a more powerful hunting rifle and even harder to conceal