If a magazine is designed to hold 10 rounds of .40 S&W but can physically fit 13 rounds of 9mm, is it legal to use in a 9mm handgun?

Question: If a magazine is designed to hold 10 rounds of .40 S&W but can physically fit 13 rounds of 9mm, is it legal to use in a 9mm handgun?

Answer options:

• No, it must be pinned to 10 rounds of 9mm ✅ Yes, as long as the magazine was designed and labeled for .40 S&W and holds 10 or fewer rounds of THAT caliber
• No, any magazine holding over 10 rounds is prohibited regardless of markings
• Only if the user has an Authorization to Carry (ATC)

Correct answer: Yes, as long as the magazine was designed and labeled for .40 S&W and holds 10 or fewer rounds of THAT caliber

Explanation: Magazine capacity is determined by the specific cartridge the magazine was designed for. If it holds the legal limit of its intended caliber, incidental capacity of a different caliber is typically permitted.