Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
Alternatively, there is a chance that they'll be obtainable in a Holo-Chest at a higher rarity, since rifles tend to be available quite frequently.
Source: https://gamerant.com/fortnite-how-get-explosive-repeater-rifle-chapter-4-season-3/