Using attachments in Call of Duty: Modern Warfare 2 might actually be making weapons worse, players believe.
Filling up attachment slots was common advice for previous Call of Duty games, since the drawbacks were negligible compared to the benefits.
But the community now thinks filling up all five attachment slots in MW2 may not be optimal, with drawbacks for many attachments not outweighing the benefits.
In other words, this is the first Call of Duty where mindlessly adding attachments may be a bad idea.
Now Call of Duty YouTuber TheXclusiveAce has done the analysis and come to the definitive conclusion - most attachments make your guns worse.
The problem comes down to the fact MW2 has massive weapon sway - when your character naturally moves the gun left and right a bit because they can't hold it straight for too long. Combined with the incredibly short time-to-kill, most attachments increase weapon sway or aim-down-sight time, which means you're more likely to miss your shots and get killed.
That doesn't mean you shouldn't have any attachments. Adding a sight to your weapon has a minimal increase to ADS time, while a larger magazine means you're less likely to be caught in a reload animation. Some attachments, such as grips, also have zero drawbacks (though with only small benefits) so you won't be losing out by attaching them.
So, the conclusion is to think carefully about what you attach, or if you want to save time, checkout Eurogamer's loadout guides.