In the recent update of the M1928 from the Halloween event, the sight was changed, and it turned out to be worse than what it was, since due to the flash of the weapon and the nature of the recoil, this sight makes it almost impossible to lead the enemy when shooting. Due to its small size in which you can barely see the enemy. Therefore, this type of weapon needs to return the sight that the regular M1928 (50) has from the upgrade, otherwise this submachine gun will be absolutely inconvenient to use.
It is a known bug