PAYDAY 2

To do this achievement, you need to play heists until the PAYDAY drop, and wait until you pick a card with the Red Dot sight attachment, and the Flash Hider attachment. Go to your inventory, find the pistol that you want, and press the button to 'Modify' the weapon. Make sure you have enough cash to craft it, and once you have modified the pistol with both attachment, the achievement should unlock.