Weapon kill challenges are the worst. In Payday: The Heist, a game not known for its balanced design, these challenges are particularly heinous. All weapons in the game (except trip mines) require a gobsmacking 3050 kills to complete their challenges, setting aside other specialized challenges. The total killcount requirement comes out to 42850 kills. Yikes.

Some of these weapons will naturally be completed over the course of normal gameplay progression. Other weapons, however, are terrible, or at least terrible to rack up killcounts with. They have low ammo pickup rates, do little damage, or are just unfun to use, sapping the will of the most hardheaded completionist. These weapons require concerted effort and hours of grinding to finish. That's where this guide comes in!

I am by no means an expert at Payday 1, but in my time working on these challenges I've learned a number of tricks and strategies that can make grinding weapon kills, especially solo, much easier. This guide describes these strats, in detail. Some I've discovered myself, many I've learned from others (with a special thanks to Frankelstner and DorentuZ, who know the game's code better than anyone and taught me all sorts of things).

This guide is a work in progress, and I'm always happy to get contributed suggestions! Just post in the comments and I'll include your tips or strategies if they seem effective.

This guide overwhelmingly focuses on First World Bank as a grinding location. First World Bank has a number of advantages over other heists:

• It's available on Easy.
  Why make things harder for yourself? Most enemies can be killed with a single headshot on easy difficulty.
  
• The Bank Manager.
  The Bank Manager is a "Perpetual Hostage"- because the game needs you to tie him down or kill him, the NPC will never escape the heist and police will never free him. In turn, this means that assault breaks last longer, giving you a nice, manageable flow of police that aren't aggressively attacking your position.
  
  
• The Copier Room Trick.
  
  This is the big one.
  
  FWB, like the other heists, uses scripted, objective-linked events to give players a sense of escalation. As the heist goes on, new spawn points open up, additional special enemies spawn, and more, stronger enemies flood the bank. This is all great, but if we're trying to manage the rate of enemies to keep a steadily growing kill counter, escalation is bad. We want low-level beat cops coming at us from as few directions as possible. How do we achieve this? Simple. Don't open the copier room. By not opening the room, 1) enemy spawn types will mostly be beat cops and FBI, with only occasional blue SWAT, heavy SWAT or Shield, 2) Tasers and Cloakers will only spawn as part of designated scripted events, 3) Bulldozers will be announced for an extended period of time, 4) one sniper position overlooking the drill won't activate, and best of all, 5) the police won't blow the windows on the sides of the building open. Instead, they'll all funnel through the front doors. (Technically, you can open the copier room and just not set up the drill, but if you do Bain gets a lot chattier.)

All of these advantages mean that FWB is usually a faster, easier mission to use when grinding general weapon kill challenges.

So get ready to have Gun Metal Grey and the intro lines forever burnt into your memory.

This is my personal favorite way grind kills in payday 1. Camping this stairway in the canteen:

is a really effective way to funnel enemies into a killzone. It takes advantage of a number of pathing weaknesses in payday 1 to make grinding sustainable for longer periods and greater progress.

First, take out guards with the weapon of your choice (I like using pistols). Then head to the stairway in the canteen and break the glass in the area facing the door into the lobby. Drop your ammo bag right under the bannister facing the doorway, like so:

Deployables in payday 1 have a hitbox that will block projectiles- yours and enemies'. This lets you provide yourself some additional cover as you face the door.

Smoke tends to be a problem for solo players, but some features of the canteen stairs make it much less of an issue. First, some general notes on how smoke grenades spawn. Only blue and heavy SWAT can spawn them, and only during assaults. The enemy pathing AI is set to spawn the grenade at a navpoint location between their current position and the player they're targeting. That's what makes the canteen stairs so ideal. While you're standing there, the navpoint between you and the police is behind you, at the foot of the stairs. if an enemy triggers a grenade, it doesn't matter!

Camping the stairs comes with another benefit- the open alcove at the left wall (under the bannister) screws with enemy targeting something awful. This is the position I'm referring to:



Enemies that are standing in the doorway and have aggroed on you seem to think they can best target you from back in the lobby. Most enemies that aren't particularly aggressive will retreat back into the lobby to try to shoot at you from there. Eventually, a blue or heavy SWAT, or a special unit, will lead a charge into the canteen- but until that point, the alcove lets you force individual enemies to back off as needed. As an added bonus, since this can be used to force enemies to come through the doorway in groups, it's especially effective for GL40 farming.


Snipers
The first time snipers are announced, it indicates that endless respawning snipers will be covering the lobby. There's a second sniper announcement, but it refers to a sniper that spawns on a rooftop window overlooking the drill. You won't hear it if you never set up the drill- this sniper will never spawn. Instead, the second set of snipers will be the ones in a row, also overlooking the drill. These enemies won't be called out by Bain, so heading toward the other side of the map is a bad idea.

"inserting special units"
This means two tasers are rapelling down from skylights almost immediately over your head. A well-placed GL40 round hitting the further taser will kill both, but it's usually more reliable to take them out with a primary weapon.

Cloakers
A cloaker announcement means that 5 cloakers are spawning- 2 through windows in the conference room over your head, and 3 from a vent in the back hallway.

Let that soak in a moment. 5 cloakers. In payday 2, that's pretty much impossible. In payday 1, it's something that happens normally on FWB. On Easy.

...anyway, I recommend rushing upstairs and taking out the cloakers as a first priority, while you know where they are. Be aware that one of the vent cloakers usually ducks onto the balcony on the left as you approach them- that cloaker will try to rush you and should be your first target.

Bulldozer
At least the first few bulldozers in a grinding session using this strategy are announced. In my experience Bulldozers almost always come directly from the lobby without circling around the back halls. I recommend always having an effective weapon on hand to deal with the Dozer- otherwise, you run the risk of RNG cutting your run short.

Sentry Turrets are hot trash, I know. Unlike Payday 2, where as of this writing they're massively OP, turrets in payday 1 run out of ammo or die seemingly instantly. But you need to get 3050 kills with 'em. What're you going to do? First World Bank to the rescue yet again!

After tying down the manager and ending guards with weapons of your choice, set up a turret as shown here:


This position is covered from most angles, and will shoot police as they go through the scripted animation of rushing through the front doors of the bank. In my experience, they usually run out of ammo before being destroyed, getting the maximum possible kill profit. After the turret runs out of ammunition, you can work on other killcounts, or just restart right away. Doing this takes a while, but it's especially mindless, since you can work on your Hox/Houston slashfiction while you wait for the out of ammo sound to play. Those 3050 kills will go by in no time many fewer hours than they would have otherwise!


You might be despairing of getting this challenge, but there's a trick. The kill "combo" carries over between attempts. Do a normal turret run, then just get killed or reset without attacking anyone. Set up the turret in the lobby again in your next run and avoid attacking again, and you'll be set.

Trip mines only need 150 kills. This makes them much easier to manage than most other weapon challenges. As an added bonus, you can shoot trip mines to set them off, which is much more reliable than hoping enemies will path through the laser.

I recommend starting the process of trip mine grind by going for the Bomb Man achievement. This will get you progress on the kill challenges, and will likely also get you the "on a trip" simultaneous kill challenges. Other guides go over this achievement in more detail; the main thing to remember is that when the security guards can't see you, they will usually gather in front of the vault, making them easier to kill together.

Short version: prioritize the most annoying weapons to retain your sanity, and keep a primary handy for sticky situations. Be willing to mix things up, and don't be afraid to, y'know, actually try to finish a heist or two when you're getting bored.

The worst weapons, imo, are: Locomotive, GL40, B9-S and Crosskill. They do low damage, are unsatisfying to use, or easily run out of ammunition. Finishing them(especially the GL40) will make the rest of the 40k+ kills a relatively pleasant experience.

Expert kill challenges are unlocked when you have only the IV challenge remaining for the weapon, or 1000 kills to go. Usually you will get this challenge in the process of clearing this last hurdle. Sometimes you might want to speed up the process, though, so this section lists good locations to farm specific enemy types or situations that can be harder to deal with.

Cloakers: Stick with First World Bank. The scripted cloaker spawn gives you 5 cloakers to massacre.

Tasers: DorentuZ` suggests Panic Room, which has a number of scripted taser spawns that can occur.

Bulldozers: You usually want to deal with Bulldozers one at a time, so FWB is actually still a good option here. Killing the manager will spawn "revenge" bulldozers on Overkill or above. If you're more aggressive, a Bulldozer is on a continuous respawn timer on Slaughterhouse- that's better pursued with a team, though.

Shields: Shields spawn quite commonly in normal gameplay, and farming scripted spawns for them is difficult, since most are inconsistent or far into a heist. Three shields will spawn to protect the manhole exit on Counterfeit. If you'd rather restart a heist over and over again, there is a strong chance that a shield will spawn at the second corner you turn in Heat Street on difficulties above Normal.