Unlocked by shooting 1,000 bullets into Time Stops. Many Time Stops are required.
Earliest opportunity to unlock: Act 1, part 2 right after you learn Time Stop. It is cumulative and, providing you shoot bullets into Time Stops throughout the game, should unlock through normal play. Alternatively, you can deliberately stack bullets into Time Stops to force the achievement to unlock early.
You can unlock this achievement as soon as you learn Time Stop in Act 1 Part 2. Equip the SMG before you open the door to Will's car. If you do not have the SMG, press
to activate Time Vision and use it to find a SMG and equip it. Note that you can use any firearm but the SMG is fastest because it can fire the most bullets into a Time Stop.
Open the door to Will's car. This triggers a scripted event. You are prompted to press
to Time Stop. When you regain regular control of Will, use Time Stop and shoot at it. The game will tell you that shooting bullets into a Time Stop will stack the bullets.
The Time Stop gauge to the right of the screen needs to recharge. Use Time Vision to identify enemy locations and evade them until the Time Stop gauge is full. Press
to activate Time Stop,
to target into the Time Stop, and
to fire the SMG.
To survive and accomplish the objective, you will want to eliminate enemies. However, for the purpose of the achievement, you just need to shoot bullets into a Time Stop whether or not they hit a target of value.
Leave the enemy near the lecture hall door alive so that you will continue in combat mode until you have the achievement. Note that you can direct a Time Stop at a car and stack bullets into the Time Stop causing it to blow up destroying any nearby enemies.
The SMG holds 144 bullets so you will need to reload. Use Time Vision to identify ammo sources. The best is a backpack against an ammo container to the right of the parking lot as you face the lecture hall door. Not only does it offer unlimited ammo but there is nearby cover and concealment that you can use while Time Stop is recharging.
When all enemies, except for the one near the lecture hall door are eliminated, continue to activate Time Stop and shoot into it. When you have shot 1,000 bullets into the many Time Stops you activate, the achievement will unlock.
Notes:
1. If you are killed before you clear the parking lot, you will revert to the check point. The check point is at Will's car just before you open the door.
2. If you revert to the checkpoint because you are killed, the game has a counter. It will credit you with the bullets you fired into time stops before you were killed.
3. The achievement is relatively unaffected by difficulty and can easily be unlocked on Hard Difficulty in the above manner.