ProMag SMI31 S&W M&P Shield Magazine 9rd 40 S&W Blued Steel

The ProMag SMI31 extends capacity for Smith & Wesson M&P Shield pistols chambered in 40 S&W, delivering 9 rounds in a reliable aftermarket magazine. This blued steel construction magazine provides shooters with additional firepower while maintaining the compact profile essential for concealed carry applications.

What Makes This Different

Unlike factory magazines that typically hold 6-7 rounds, the SMI31 increases capacity to 9 rounds without significantly altering the pistol's grip length or concealability. The blued steel construction offers enhanced durability compared to polymer alternatives, with heat-treated steel components designed to withstand repeated loading cycles. ProMag engineers this magazine to function with standard 40 S&W ammunition weights from 155 to 180 grains.

Key Features

• 9-round capacity for 40 S&W cartridges in S&W M&P Shield pistols
• Blued steel construction with corrosion-resistant finish
• Heat-treated steel spring maintains consistent tension over time
• Anti-tilt follower design prevents feeding malfunctions
• Removable floorplate allows for cleaning and maintenance
• Compatible with M&P Shield models 11905, 180020, 180021
• Drop-free design ensures reliable magazine changes

Range testing demonstrates reliable feeding with popular 40 S&W loads including Federal HST, Speer Gold Dot, and Winchester Ranger T-Series ammunition. The magazine functions consistently in both controlled pair drills and rapid-fire strings, maintaining proper lockback on empty. Law enforcement officers report successful deployment in qualification courses, while competitive shooters appreciate the extended capacity for IDPA Stock Service Pistol division matches.

Technical Specs

• Capacity: 9 rounds
• Caliber: 40 S&W
• Material: Blued carbon steel body
• Spring: Heat-treated steel wire
• Follower: High-impact polymer with anti-tilt design
• Overall Length: Approximately 4.2 inches
• Weight: 3.2 ounces empty
• Compatibility: S&W M&P Shield 40 S&W models
• Finish: Traditional blue oxide coating
• Country of Origin: USA

The SMI31 addresses the capacity limitations of compact carry pistols without compromising reliability or adding excessive bulk. ProMag's established reputation in the aftermarket magazine sector, combined with the robust steel construction, makes this a practical choice for shooters seeking increased ammunition capacity in their M&P Shield platform.