Warne Mag Ext S&w M&p 9/40 +5/4

The Warne Mag Ext S&W M&P 9/40 +5/4 is a magazine extension designed to increase ammunition capacity for Smith & Wesson M&P pistols chambered in 9mm and .40 S&W. This accessory adds either five rounds (9mm) or four rounds (.40 S&W) to standard factory magazines, extending both the physical length of the magazine and its overall round count without requiring a completely new magazine body.

Magazine extensions function by replacing the factory basepad with a longer aluminum or polymer extension that maintains magazine geometry and feed reliability. The +5/4 designation reflects the caliber-specific capacity increase—the 9mm variant adds five rounds due to the smaller diameter cartridge, while the .40 S&W version adds four. Installation is straightforward and requires no gunsmithing, making this an accessible upgrade for shooters seeking higher capacity. Warne's design maintains compatibility with standard S&W M&P holsters and accessories, though extended magazines may require holster adjustments or may not fully conceal in certain carry configurations.

This extension is practical for shooters running higher-round-count training drills, competition stages, or those who prioritize spare ammunition capacity during range sessions. Law enforcement and armed security personnel often use magazine extensions to standardize capacity across duty and backup magazines. The product suits anyone operating S&W M&P pistols who wants to increase round count without committing to aftermarket magazine systems, providing a cost-effective upgrade path for existing factory magazines.