How exactly do I obtain a modification for a weapon?
I know how to modify a weapon, but I've yet to find something to modify it with.
All help is appreciated, thanks.

Wut?

Like, adding scopes and barrels, silencers and what not, I know you can do it. But I haven't found anything to add onto a weapon, comprende?

gun runners carrys a good amount of gun mods

the sliver rush, carrys a large amount of energy mods

and the boomers carry alot of explosive mods

I just purchase them from them? Really? If it's that easy I really feel stupid.

Check every merchant that sells ammo/weapons, most of them carry gun mods from time to time. Which mods show up will be random, so keep checking back after letting the merchant's cell lie fallow for 3+ game days.

Check any merchants "Misc" section.
After you've bought one for the weapon you use then press LB on 360 to install it.

Anyone know how to upgrade on PS3?
Bought tons of upgrades, can't seem to use 'em.
Thanks

When you're in your weapons inventory the button to push to repair and the button to push to mod the weapon are at the top right. At least it is on PC.

Chet in Goodsprings has a scope and silencer for the Varmit rifle, relatively inexpensive (100-150?). As stated previously, just check out the Misc section and hope to get lucky!

Chet also sells extended mags from time to time for the Varmit rifle as well as extended mags for the 9 mil pistol as well as a scope for the 9 mil pistol. I bought the silencer, night vision scope for the varmit rifle form chet as well as the 9 mil pistol scope.

I have to say that Varmit rifle with armor piercing rounds and thenight vision scope made for wonderful night time sniping of ghouls.