Years after Twitter replaced the pistol emoji with a green-orange water gun, X decided to change it back to a regular pistol. X employee announced the change in the post last week.
Emojis are universal because they share common names across platforms (U+1F52B is water gun), and these names are determined by the Unicode Consortium. But it’s up to each platform owner to decide how to represent it visually. That’s why we addressed the cheeseburger emoji debacle in November 2017.
If you look up X on the web, you’ll only see this gun – as of this writing, it doesn’t appear to have been updated in the mobile version of the app, although that’s apparently being updated at some point.