*************MUST ALL BE DONE IN ONE PLAYTHROUGH**************
I learned this the hard way as I had spread them across multiple runs. Therefore, this is better to do solo IMHO. Just play a solo match on Regular.
Rather than just give a list of weapons and their locations I thought I'd give folks a run down of the easiest way do this solo for those that struggle playing solo, as well as more detailed directions to each weapon.
At the start, run around and open regular boxes and hope you get a locker key. This isn't 100% necessary but makes it much easier at the beginning.
Now for reference sake, there are 3 weapon schematic spawns. The will NOT always have schematics, but these are the 3 locations they can be at.
Number One is to your immediate left as you exit the tunnel at the start if you hug the zone wall. Facing out from that one, #2 is straight across the ravine as you round the first bend in the trail when LEAVING #1. Number three is pretty far from the exit tunnel, but if you exit the tunnel and turn to your right instead of left and hug the zone wall, you will run into it.
Spawns 2 and 3 ALWAYS spawn a Mammoth.
Once you've opened boxes and got a key, or some incendiary or explosive ammo or what not, head back to the cave exit you first come out of and head to Schematic Spawn #1. Either scorpions or a Rhino will spawn here every time. Kill the Rhino (or scorpions) and look for the Ark attachment, or a Venom X weapon schematic, or both if you're lucky.
If you get ah Ark attachment you can ignore spawns 2 and 3 entirely. You can either restart if you don't get the Ark attachment here if you have a hard time fighting Mammoths, or if you get the Venom schematic (or are really good) and want to you can continue on. If you choose to, build your Venom or kill an obelisk or two for some funds for a good weapon, then head to spawn 2 and use it to kill the Mammoth and check for the Ark. If it isn't there head to spawn 3. It will always be in one of the 3 spawns.
Once you have the ark, if you only killed Spawn 1 you may not have enough $$ for a weapon. Whenever you have enough cash, start buying the weapons, starting with the cheaper ones and working your way up. I do advise doing the VKS first to get it out of the way since it's a sniper and they're kinda a PITA if it gets hectic with lots of enemies.
You can get all the weapons in the first area save for the USR and Bulldog. I'm putting them in the order I suggest for utility and ease of use, and the expensive ones last since you can get infinite $$ during the final phase of area 1.
1. VKS - From the entrance tunnel, take an immediate right and jump up onto the small ledge. Follow up the cliffside. You will pass the TAC 12 auto shotgun and see an Obelisk above you. Past the Obelisk is a ledge with a 'mushroom' below it. The VKS is in the small ledge area in front of this before the next zone-wall Obelisk and can be jumped up to from the ground or from this mushroom.
2. TAC 12 - See above. Just head back along the zone wall and grab it.
3. Ripper - Facing the Exit from the first area, look to your right up against the wall and you'll see it pretty near to the exit door.
4. K7 - Facing the Exit from the first area, look to your left and you will see a small ledge. Jump up onto this ledge and you'll find the K7 semi-hidden in the weeds.
5. IA2 - Standing at the exit of the tunnel at the beginning and looking straight out, you will see a ramp like rock structure that ends in a ledge. To the right of this you will see two of the big mushroom tree looking things. Not the ones growing out of cliffs, but the free-standing ones. They are at about the one-oclock and two-oclock positions when facing straight out from the exit. The IA2 is below the left one (one oclock one), the one that has an Obelisk to the left of it from this perspective.
6. Remington - Coming from schematic spawn area #2, hug the zone wall on your left to the end of the ledge as you come back out into the open area and you'll find the Chainsaw on the wall to your left. Drop down straight ahead of the SAW into an orange-tinted cave. It's in here against the wall.
7. MK14 EBR - Go to the ripper and face the wall where it is located. Now turn 180 degrees and look to your left. You will see a tall stone pillar that connects to the cliff above (there's one to your right too). The MK14 is behind this left-hand pillar down over the ledge on a lower ledge.
8. Chainsaw - see the Remington above. It's on the small ledge above the Remington's cave between it and schematic spawn point 2.
9. Ameli - Face the zone exit up against it, then turn around 180 degrees. Head down the slope until it levels off and you see a small raised piece of rock roughly diamond shaped in front of you. Now look slightly to your right up against the wall at your 1-oclock and you'll see it at the start of the 'ravine' like area in the middle of this first portion.
10. Maverick - Saved the best for last, but you can do this one earlier as it's one of the cheaper ones. Just head back to the entrance tunnel at the very beginning. It's on the right just before you exit the tunnel, hard to miss.
AREA 2 --
11. USR - It is up against the wall right opposite the predator control laptop.
12. Bulldog - When you exit the tunnel coming into area 2, turn 90 degrees to your right and head up the nearest Obelisk on the higher ground (this is the same direction you'd head to go to the predator laptop/USR). A little further ahead on a ledge overlooking this Obelisk is the Bulldog.
A couple of tips:
If there's a gargoyle out, just ignore it and hide under a ledge/mushroom/etc near the Obelisk and deal with the smaller enemies. The gargoyles, when they're high up, will likely waste your ammo and maybe even kill you or get you killed by smaller enemies. Eventually they'll come down and walk near you allowing for an easier kill. Or deal with them after an Obelisk is done and the other enemies are dead.
Also if you have a Venom weapon use it liberally if you get into trouble. You'll get plenty of ammo for it and worst case scenario you can farm ALL the kills in area 1 with ALL the weapons except the USR and Bulldog during the final part with the predator as the enemies spawn infinitely.
Lastly if you do happen to go to more than one schematic spawn area, look for sticky flares even if you don't get a Venom schematic. They can save your bacon, and if you're down to the last weapon or two at the end of area 1 or the USR/Bulldog in area 2, it would suck to fail.