Warhammer 40,000: Space Marine
35 Achievements
Firepower
Kill 250 enemies using Exotic weapons.
2.2%
How to unlock the Firepower achievement in Warhammer 40,000: Space Marine - Definitive Guide
These weapons can be fired from their mounts by pressing (B) and can be ripped free by pressing (X).
Get 250 Kills with these weapons to unlock the achievement.
********* Spoiler Below *********
The best place I've found to achieve this is in Chapter 13.
You'll encounter a psyker who opens a Warp Gate and summons an infinite number of Traitor Guardsmen.
In the same room with the psyker is an emplaced Heavy Bolter. Rip the Bolter off the mount and you should have 300 rounds to kill the Traitor Guard.
Stand behind one of the tall pipe/pillars in the room in such a way that you can see the gate where the Traitor Guard spawn and the psyker can't hit you with lightning.
It only takes one round to kill a Traitor Guard and they spawn about every second or so. If you're light on the trigger, you'll have plenty of ammo to reach 250 kills for the achievement.
If you don't get it on the first try, just reload the checkpoint and repeat as this will not erase your kill total.
This is right before you pick up the Stalker Bolter for the first time
After getting the achievement, the choice is yours to finish off the Ork here and move on ... or you can reload the checkpoint and work on
since you had just received the skill after you met up with the lieutenant at the bunker.
Exotic weapons consist of anything that's on a tripod. The Heavy Bolter and Plasma Cannon come to mind. Just kill 250 of them throughout the game with any weapon that's on the tripod.
A good place to grind this out is at Chapter 2 at the 'Trenches'. There's a mounted Heavy Bolter near Orks will come in. Simply use this spot to grind out, reload a checkpoint and repeat.
Another good place for this is in chapter 14 using the Autocannon. (Thanks c1ned1ne!)
'Exotic' weapons are any weapons that are mounted on tripod. You can find a Heavy Bolter and a lot of Orks in Chapter 2 where you can grind it out, and there are Plasma Cannons on Chapters 4 and 7 or 8. Mounted Autocannons can also be found later in the campaign. These weapons can be ripped off of the turret mount to carry around during the Chapter. For most turrets this disables its infinite ammo.
To grind this out, simply go to Chapter Select under Single Player, select Act 1, Chapter 2, and the section labeled "Trenches". Play through the Chapter until you reach the Digga cutscene where Ork machines bust up through the ground into the Imperial Guard trenches, then continue around the next few corners until you see a mounted Heavy Bolter. This is the location you want, as you can net somewhere between 30 and 50 kills after grabbing the Heavy Bolter. Once you gun down the horde, simply reload the checkpoint, run back around the corner, and begin the process again.