The AAC Integrally Suppressed Remington 700 is an American sniper rifle manufactured by Remington Arms. It is a modification of the R700 that has an integrally suppressed barrel. It appears in Battlefield Hardline as the .300 Knockout, where it fires the .300 Blackout round.
— In-game description
It is distinct from the Professional's other rifles in that it is integrally suppressed, meaning it has a permanently attached Suppressor. This gears it more towards close and medium range engagements, as the suppressor causes a large amount of drop compared to the other rifles. However, it still has very high damage, allowing it to still perform effectively at long range if the player accounts for bullet drop.
In January 2016, the .300 Knockout was nerfed. But it was different on Consoles and PC. On Console as well as on PC, the rate of fire was reduced by ~30% making it harder to fire successive shots. Only on PC, the Knockout and all other available sniper rifles were significantly nerfed, making it impossible to kill an enemy in a single body shot unless he was injured before, however the minimum damage remained the same meaning you are still able to kill an enemy with a single hit to the head with the .300 Knockout.