You may have noticed that the term “bloom” comes up in several Halo: Reach articles and videos. You don't have to search for a particular setting to turn it on or off in your options menu. Instead, it has to do with your weapon's reticle.
Bloom occurs in your game when you continuously fire your weapon in a single period. You will notice that the reticle on your screen becomes slightly larger than when initially shooting. Shots that occur one after another become inaccurate because your weapon moves, reducing your overall accuracy.
If you want to reduce the amount of flowers in your weapon, you should perform accurate shots at separate intervals, not immediately one after another. By waiting to pull the trigger on your DMR and pistol, your shots are more likely to hit their target. Not only will they be more likely to hit the target, but you'll likely hit the spot you were aiming for, like getting those perfect headshots.
Unfortunately, your options are not set up to help you achieve this. You need to take the time to make your shots count and learn how each gun fires. To do this, observe the reticle of your weapon and determine when the reticle returns to normal. You should also notice how many moves you can make before it becomes inaccurate.
You can practice this by playing Firefight or relying on Halo: Reach campaign on an easier difficulty before going online to fight competitively.
