Make Every Bullet Count Achievement
Make Every Bullet Count25
Complete a mission with 100% accuracy, using only riflesYou need to use your rifle exclusively to get this achievement. You cannot unlock this in the 'Prologue' if you have the tutorials turned on as at one point it tells you to use your silenced pistol to take out an enemy.
After you have finished the 'Prologue', go back to the main menu to turn off the tutorials by navigating to Options > Game > Tutorials (on/off). Then go back to the main menu and select Single Player > Mission Select > Prologue. Select 'Cadet' difficulty for ease and start the mission. It will start right when you are to shoot the Major-General.
If you are careful, you should only be shooting 3-4 enemies. Take your time, make sure that you have a clear shot at them and kill them with the first shot. If you follow the video in Hide and Hope (10G), you really should have no issues unlocking this and that achievement at the same time.
Note: Reloading checkpoints does not void this achievement.