Do you pronounce "primer" with a long or short "i" sound?
More specifically, it depends on which meaning of "primer" you have in mind. If you are referring to a first coat of paint or a blasting cap, use a long "i": the vowel sound found in "pie" and "high." If you're referring to a schoolbook, the preferred American pronunciation is with a short "i": the vowel sound found in "it" and "big."
—The Fact Monster