Weapons in Resident Evil 4 Remake can be upgraded through different attachments to improve and customize various tools players find throughout the game. Although various attachments are only compatible with certain weapons, players can still get these tools multiple times and apply them to nearly every gun they encounter. Ranging from scopes, stocks, and even sensors, players have a better chance to overcome the hordes of Ganados enemies in the story using these upgrades.
https://screenrant.com/how-to-find-every-weapon-attachment-resident-evil-4-remake/