After playing the 1999 mode and scavenger hunt, I decided to make a little guide to help other people trying to get these achievements. Obviously, this guide will be written based on my own play style, meaning that it may not apply to many players. I will not make a step-by-step area walkthrough, but I will give you a few advices on general gameplay tips, for example: what weapons to use, which to avoid and how to deal with certain enemies. On a last note, sorry for any English mistakes.
About the Achievements
The 1999 mode turns up the game difficulty by a considerable amount, especially if you just played the game in normal or easy. The enemies do a lot more damage, are much more accurate and are authentic sand bags, meaning that they overall take very little damage, even the weaker enemies. They will very easily swarm you and kill you. Also, there is less ammo available, less amount of coins to be looted and your shields take longer to charge. To add up to this, every time you need to respawn, you are charged 100 coins, plus all your enemies in that area are healed. In case you do not have enough coins, you are not revived and are sent back to the main menu.
The Scavenger Hunt achievement can be won by not buying anything from the Dollar machines while beating the game in the 1999 Mode. Considering that enemies require much more shots to be killed, that brings up yet another setback to deal with, since you will need more ammo than usual.
Early Choices - Shields, Health or Salts
When deciding what upgrades to take in this mode, there are a few things to take into consideration. While each health upgrade gives a considerable amount to health, when compared to the shields, the later repair themselves automatically and do not need any pick up to be replenished. That alone makes the shields much more valuable than health in the early game.
However, the early game is marked by difficult enemies and enemy waves, while the player still does not have any particularly strong weapon. One of the easiest ways to deal with these enemies is using vigors, particularly Possession. While fighting tougher enemies, in this case the Fireman, Possession should be used on him. He will proceed to eliminate the weaker enemies that would otherwise be harassing you and while he is at it, you can spam him down with your pistol/machine gun. The disadvantage of this method is that enemies under Possession’s effect take less damage, so it will cost you more to kill them. On the other hand, they don’t fight back, making it much easier in the early fights to dispose of them, while retaining health.
I would recommend choosing two shield upgrades, followed by two salts upgrades and so forth, until reaching the 7th salt bottle (included). After this, level up your shields to the maximum and finally start taking health upgrades.
A few vigors are very important in this game, almost indispensable. And some upgrades, while very expensive, make the game much easier.
I would advise buying, as soon as possible, all upgrades to Possession. Possession is single-handedly the most important vigor in the game. In the early game, it will help you clean out areas with smaller enemies, by using their own turrets against them or Firemen. Also, instead of wasting precious ammo to deal with the turrets, you should use Possession on them. In this mode, turrets take very little damage, it is much easier to make the enemies destroy them or simply avoid them when possible. In the later game, Possession can be used on tougher enemies, like the ones that carry heavy armour and stronger weapons. Not only do they become strong allies, it also eliminates the necessity of spending heavy amounts of ammunition trying to kill them, as they commit suicide at the end of the vigor’s effect.
Murder of Crows is also essential in this mode. It should be upgraded right after Possession. While the “Crows Trap Aid” upgrade is facultative, it does help save salts in the later game, while facing waves of enemies, as dead enemies become crow traps and simply infect other enemies coming by. “Crows Boost” upgrade is essential, it increases the time of stun and makes fighting the Handymen an easier task.
“Bucking Bronco” is incredibly useful while fighting Zealots of the Lady (aka Crows), but does not require any upgrades. It can be used to stop hordes of enemies on their tracks instead of “Murder of Crows”, since it requires much less salts. I personally prefer to use the Crows, since they create new traps. Ultimately, the Crows can use less salts because of this.
You can ignore the other vigors completely.
What weapons to Use / Upgrade
I think this may be the most controversial area. Since the enemies have very high damage and damage resistance and our ammunition is scarce, I prefer using weapons that cause high damage per bullet. Also, I recommend having one main weapon always on you and exchanging the secondary weapon based on ammo availability. Regarding upgrades, fully upgrade your main weapon, the rest of the weapons you want to use upgrade only the damage. You don’t have much money in the game and the damage is really the most important. While reload speed and accuracy make for interesting upgrades, you can achieve the same thing with good reload timing and aiming skill.
Sniper Rifle. No doubts here. The sniper rifle allows you to take most enemies with a headshot, especially when using the “Head Master” gear. This means that you can take enemies down while exposing yourself only a little for each shot. Making each shot count is important, as the sniper rifle has little ammo available and you will depend on looting/Elizabeth’s drops. So, use it with care and try to always keep some bullets on you at all times, especially for the moments when enemies come in waves, in order to never run out of ammo. What I mean with this, is that you should keep at least one or two clips spare for rainy days, in which case you should change for your secondary weapon. Also, don’t forget that even without the scope, it has 100% accuracy, so it can easily be used at close range. You should upgrade it completely.
Carbine. The carbine shares many similarities with the sniper rifle. High damage per shot, high critical hits. It has more ammo available during the game, even from enemy drops. Plus, it might be easier to use at close range. Don’t use the iron sights, as it makes handling the weapon much harder. If you are running low on cash, upgrading the damage alone is enough. Make sure you aim for headshots, or else you will easily run out of bullets.
Repeater. With completely upgraded damage, the repeater is a very strong weapon. It has much better accuracy than the machine gun and decent amount of ammo available later in the game. I rarely used it, but it saved me on the last stand at the end of the game.
Shotgun. Mostly useless. I put it here, however, because in some moments in the game, enemies won't carry anything else. If in these situations you run out of ammo, you might not have another choice than to use a shotgun dropped by an enemy. Because of this, I recommend upgrading the damage of the shotgun, but avoiding use it altogether. For any real damage to be done with this weapon, you need to be close to the enemies. In this game mode, being close to enemies is what you do NOT want.
Volley Gun. Because of the way it shoots and rarity of the ammo, this weapon should be ignored, except in three/four particular situations: the Handymen encounters. In my opinion, this is the best weapon for the Handymen. They are always in the area when they spawn and so you don’t need to carry them. For this purpose, you don’t need to upgrade them either.
Situational Weapons (you ran out of ammo, there is nothing else available):
RPG. Hand Cannon. I recommend buying at least the first damage upgrade for the RPG, especially later in the game, when you will start having money after upgrading all the rest of the important things. Both weapons deal decent damage, but are not good to be carried around with you. Take them when you are out of ammo, or trying to save the ammo you have, then trade them for your weapon back.
Useless Weapons (100% avoid them):
Pistol. Only useful at the start. While it does good damage and has excellent accuracy, the damage will not be high enough to stop an enemy from getting close. You might find yourself having to spray them down. For this reason, I always ran out of bullets quite fast and started to ignore the weapon altogether.
Heater. One shot per reload. I mean, short range and one shot per reload. Would be useful if the enemies formed a line and calmly approached you one by one and waited to be shot to the head. As such, avoid this.
Burstgun. It shots 3 bullets, with high recoil. The three shots together do as much damage as one carbine shot. Except that at long distances two of them usually hit nothing and even at close distances it is hard to hit three headshots per burst. There is no reason to be using this over the carbine.
Crank Gun. Fun to play, but the few moments before actually starting the shoot means that you are exposed, the low damage per shot and the low ammo available renders this weapon mostly useless. It has high burst damage, but I would still prefer two headshots from the carbine rather than a full spray of the Crank Gun.
Hail Fire. I honestly didn’t use it once. It has very limited ammo, which is a problem in the 1999 Mode.
Melee. You don’t want to be close enough to enemies to be able to use melee attacks.
Handyman: this enemy is fast, tough and deals a lot of damage. On top of that, he can easily chase you across the map and on skylines. Plus, he is usually followed by a few other enemies. Every time he shows up, there is a Volley Gun around and ammo for it. Pick it up, then get close to the enemy and use “Murder of Crows”. He will be stunned, which will allow you to spray him with the volley gun. Don’t try too hard to hit his heart, but do shoot him from the front. Keep him stun-locked and you can easily take him down this way, without taking any damage. Make sure you know where are salts in the map, in case you run out. In that case, quickly disengage, go for salts and stun-lock him again. In the area of the game, right before you fight the siren, there are other enemies. I recommend you take the volley gun immediately, then go to the balcony on the lower left side (next to where you enter the area). Other enemies don’t have visibility to that area, which allows you to 1v1 the Handyman.
Firemen: until you have “Murder of Crows” vigor, use “Possession” and spray them down. This method consumes a lot of ammo, but keeps you safe. Also, if there are other enemies nearby, they will either kill him, or get killed. Either way, it’s a win-win for you. Later in the game, once you have “Murder of Crows”, take him down as any other enemy. Don’t forget to aim for headshots.
Zealot of the Lady (crows): “Bucking Bronco”, even when not upgraded, is incredibly useful. It lifts them up and you can easily land critical hits. Otherwise, in the beginning of the game, you can use “Possession”, although as stated before, that method spends a lot of ammo.
Motorized Patriot: use your sniper rifle to land headshots, then use your secondary weapon to spray down the gears. If there are other enemies around, try to either use Possession on them or on the Patriot. Either way, damage will be done. I did not find any specific way to deal with them. They are easy to avoid and when engaged from a distance, they aren’t so strong.
Siren: for this fight, you need the upgraded version of “Murder of Crows” and a carbine. Stand behind the mausoleum (across from the entrance, behind where the lady Comstock was resting before), use the vigor on the resurrected enemies and dispatch them with carbine headshots. They will create crow traps on death. Since you are at the end of the map, the enemies must walk on those traps and get stun-locked, allowing for easy kills. Use the moment when the ghost is reviving enemies to shoot her. Do NOT aim for headshots on the ghost. She has a strange hitbox and for some reason, many body shots became critical hits anyway. Don’t worry about the salts, Elizabeth will provide you. If she gives you ammo instead, it is even better. The traps from the dead enemies will be enough and since you are hiding behind the mausoleum, the path to you works like a corridor, making headshots easy to hit. It did not happen to me, but make sure that you are not flanked from the right side. The subsequent fights with the Siren can be handled in a similar fashion: in the bank, simply stay inside of the vault. Use the crows for the minions and dispose of them as you did before. Since the vault entrance gives you more protection than the building in the graveyard, this is an easier fight.
Positioning is important in this game. When facing a lot of enemies, using the cover at the very entrance of the area makes the fight much easier. You sacrifice the weapons, salts and health packs scattered through the area during the fight in return for protection. However, you are much less exposed, you can cleanly use your rifles and prevent enemies from getting closer. Plus, at the end of the fight you can scavenge the area and loot everything anyway.
Do not fight the turrets. If there are enemies on the area, use Possession on the turrets and the enemies will kill them. At the entrance of the police station and in many other areas, when there are two turrets next to each other, use Possession on one and they simply destroy each other.
Backtrack for using lockpicks and grabbing other items. It is generally worth fighting one horde of enemies in exchange for items you left behind, for example the chest that is opened with the key that you found inside the church (or whatever that was), where the crow people worship.
Always aim for the head. Even if you fail a lot of shots at the beginning, continue to always aim for headshots. You will eventually get used to it and start doing it automatically and it makes the game much easier. Plus, you start saving ammo, which is important later on.
Do not revive. If you die, simply restart the checkpoint. It will save you 100 coins, plus there is no advantage in reviving anyway, except saving yourself some time. The enemies get their health back completely, you don’t, plus you lose money. Just restart the checkpoint, try again, try to change strategy or position, try to deal with the enemies differently, etc. You can pass the entire game without needing to restart.