the end game quest???? i was reading on the wiki, and it says it isnt available untill the end game quest. any conformation on this?
No. Ranger vets will start spawning when you start the first endgame faction quest. For instance, the first Wildcard quest, the first NCR endgame path quest, or the first Legion quest.
Then you just have to find a ranger vet and kill them.
Or, you can try the old reverse pickpocket trick. Or lure giant radscorps/deathclaws/etc to the ranger vet and let the monster do your work for you.
Also, if you murder a ranger vet and nobody sees you (ie you sneak), you
shouldn't lose any faction rep with the NCR.