UPDATE: Infinity Ward Senior CM has confirmed on Twitter that a fix is ready to go for this and will be released soon.
Drift0r (@Drift0r) October
We have a fix ready to go for this.
Williams (@ashtonisVULCAN) October
An odd bug has been identified in Call of Duty: Modern Warfare by users across Reddit and on Twitter about using weapon charms in Call of Duty: Modern Warfare.
Per images and videos shown on Reddit and Twitter, using weapon charms on your weapon in Modern Warfare makes your hip-fire aim worse, which results in potential to miss more shots.
Here’s the image showing the difference by Reddit user u/JustFuckMyShitUpTbh:
It would be wise to avoid using weapon charms till a fix is in place.