Here is the full list of all 13 Reloader: test_subject achievements.
Learn how to reload.
Escape from the Building.
Escape from the Building without breaking a lightbulb
Finish game with Reloader mode.
Finish game with Bullet counter mode.
Defeat enemy with two shots to the body.
Defeat inhanced enemy with two shots to the body and one to the head.
Defeat three enemies with head shot in a row.
Execute close combat with injured enemy.
Switch new magazine when bullet in chamber.
Finish game without fixing slide back.
Finish game with keeping concentrate over 50%.
Use tactical targeting.