One shot, one kill - repeat

One shot, one kill - repeat is an achievement for killing 30 people, including civilians, in 30 consecutive shots using only the M308.

The M308's red dot sight, which is unlocked at level 31 of the Sharpshooter tree, is recommended for improved accuracy.

Methods

• Start a solo game with no team AI on easy difficulty in First World Bank, carefully kill the security guards with one shot each, and then massacre all the civilians. You should only need to kill a few law enforcers afterwards. This also works on Panic Room on normal difficulty without starting an assault which instead of security guards you take out all the gangsters, after this you can kill Chavez and a couple civilians.
• After starting the saws in the Panic Room, go to the third-floor balcony. From this stage of the heist and onwards, four cops will take position behind the police cars that are in front of the building, and then never move. When one of them is killed, a Blue SWAT will take his place shortly, even when there is no assault. This can be done after the saws have detached the panic room, but would be more difficult with the larger number of enemies and entry points.
• Massacre all the civilians in No Mercy. Most of them can be found in the reception and the cafeteria. If you are quick enough, then you can kill them all before the first cop arrives.
• Kill the civilians on Heat Street. There are many between the beginning of the heist and the crashed van, and they are easy targets after being shouted at. The achievement can even be unlocked without killing any law enforcers.