Lyper,
If you’re hunting with the Opalo/103 amp combination, I’d like to suggest my favorite spot. Go east from Port Atlantis until you run into the combibos/exarosaurs. Stay and kill until you’ve ran through your ammo. (I’d suggest hunting w/ a larger amount of ammo – 100PED or more; also helps to have an extra 103amp handy, as you run out of durability on the amp at around 5500 ammo through the Opalo w/ the 103). I’ve done 3, 100 ped runs in this area, and have only been unprofitable one of those times, and even then I only lost around 10PED. Sweating those mobs can also make the hunt less costly or more profitable. I’ve gotten some nice loots from them too, including a 68 ped global. Once you’ve skilled to about 1.5k rifle, then consider hunting the corns that are NE of Ft. Argus, and if you have good armor and FAP (Rascal armor, FAP-50 for combat, FAP-5 for non-combat), then try your hand at the Argonauts that are in the mountainous region northwest of Twin Peaks.
Good luck friend, and Happy Hoffing.