I seem to be running more and more often into issues like this:
The weapon model loads all messed up and the sights are ruined. Seems to be particularly happening with US.
I used to have this happen with planes. It would not load the entire cockpit skin about once a match, so I had full FOV vision. It was super annoying because there was no frame of reference and made it more difficult to fly.
Since I uninstalled the original launcher and reloaded the Steam version, this has not happened. Maybe try reinstalling?