Do merchants restock? If so, how often?

[scratchm]

So I just got to the Gun Runners on my second playthrough, and the vendortron has nothing but complete drek. It's pathetic. If I wait a few days will they eventually stock different guns, or am I kind of screwed? Is there anywhere else to pick up good Guns guns? In particular I was hoping for the .50 cal sniper rifle.

 

[Ausdoerrt]

According to the Vault:

The Vendortron's stock is updated on Sundays and Wednesdays.

http://fallout.wikia.com/wiki/Gun_Runners_(Fallout:_New_Vegas)

Seriously, the Vault usually has info on all of these little details.

 

[vanzizzle]

Oh, Contreras at Camp McCarran sells a lot of ammo and high level guns. Be sure to have good reputation with the NCR though otherwise you're sure to get ripped off.

 

[Guardian of Nowhere]

If you're desperate to convert your heavy loot to caps and don't mind glitching, you can make the traders restock instantly. Just autosave in front of the trader (didn't seem to work long distance somehow), exit the game, restart, continue from autosave et voilà, new inventory (on PC, anyway). Rinse/repeat.

Probably not what Obsidian had in mind, but since I have this strange urge to take everything I see with me and also to become incredibly rich just in case I need to be, this works for me.