If you're aiming for the highest damage per bullet, you should have a look at the Railway Rifle. It starts out with considerably higher damage unmodded in comparison to the Hunting Rifle.
However, you might feel it has a very "un-snipery" feel to it because it does not look in the slightest like a weapon made for sniping in the usual sense. In that case, yes, the Hunting Rifle is your best bet. I had no raw one at hand, so here are the fully modded stats of a Lucky Hunting Rifle with all damage and sniping components:
I would look thoroughly for a rifle with a good legendary mod though, seeing as 139 damage is pretty meagre in higher difficulties. Aim for one of these: (somewhat in order of expected payoff)
- Instigating: Does double damage if the target is at full health.
- Two shot: Fires an additional projectile. Decrease in accuracy.
- Junkie's: Does increased amounts of damage the more withdrawal effects you are suffering. (if you're into chems. I read the damage goes up pretty high)
- Mighty/Powerful: Deals an additional 25% damage.
- Lucky Weapon: Critical shots do double damage and the critical meter fills 15% faster. (If you're into using V.A.T.S.)
- Penetrating: Ignores 30% of the target's damage and energy resistance.
Ammunition did not pose a problem for me. As you can see on the screencap, I have ~1200 shots. Another 1500 are on Nick because I gave him a similar weapon. A clip for the best magazine mod holds 10 bullets if I'm not mistaken, with which, when looking at the Fire Rate, it generally takes FOREVER to deplete 1000+ rounds.
Also, if you pick up the Scrounger perk (additional ammo found throughout the world), you will find boat loads of .50 ammo. This stuff is everywhere and I have absolutely no use for it. Maybe it's just a troll and you'll find plasma cells when you're using that Hunting Rifle, who knows...