I have only modded oblivion before so I'm making an educated guess but I would say yes, you can. Though it is not always recommended to overright existing guns. Its a much better idea to copy a gun then edit the copied version so what you change isn't permanent.
If youre refering to the feature in the games called "Modding" where you buy an attachment for you gun, its as simple as that if you can afford the attachment (Mod) then you are able to apply it to the designated weapon.
Unique weapons cannot be modded like regular weapons. 'That Gun' is already a modded .223 pistol, you can't add any other weapon mods to it.
You can't. Once you put it on it says on
The unique weapon you want is located in vault 34, the gun is in the armoury there and is called the All-American.
Occasionally Fallout: New Vegas will freeze, but not as frequently as Fallout 3.
Some of the content was not put in by obsidian and the game cannot load the content and the xbox freezes.
The only one I can think of is the Sleepytyme, with the gun runners arsenal pack
fallout: new vegas 2 I've heard.
Fallout New Vegas is the fifth installment in the Fallout series. It is for the Xbox 360, PS3, and the PC.
In my opinion, Fallout 2.
Fallout new Vegas
No, you can't get married in Fallout: New vegas, but you can have sex in the game :)
Fallout: New Vegas