I carry a silenced .50 hunting rifle and a six crank laser musket. The .50 is what I use most of the time because it has a higher rate of fire, more bullets before reloadin and I can use it in close quarters without alerting enemies. It's the only .50 cal gun in the game worth using and since it also does higher damage than .308, I never run out of ammo for it. I tried using old faithful as a laser sniper rifle before and it's probably more ammo efficient than the laser musket, but it just doesn't work for me. Scopes block the little 3 light charge meter (I think that's what it is), so I can't tell when I'm at full damage.
By the way, it took me a while to figure it out, but the laser musket reloads waaaaay faster if you mash the reload button.