Warne 3306 Magazine Extension Black, +3 9mm Luger, +4 .40 S&W for S&W M&P 9/40

The Warne 3306 magazine extension for S&W M&P 9/40 gives you the extra capacity and control your duty or carry pistol needs. Designed to add three rounds to your 9mm magazines and four rounds to your .40 S&W magazines, this extension lets you carry more ammunition without changing your platform. It's the kind of upgrade that matters when every round counts—whether you're at the range, on the job, or in the field.

Built from 6061 T6 aluminum billet and finished with Type 2 hardcoat anodize, the Warne 3306 is engineered to survive hard use. The anodize protects against abrasion and corrosion in all conditions, while the ergonomic design and finger grooves make the magazine easier to strip from your handgun when you need it—a practical detail that separates thoughtful gear from afterthought parts. A Torx head screw and washer keep everything locked in place without fuss.

Warne built this extension right here in the USA, which means you get the precision and quality control you expect from a company that knows firearms. If you're running an M&P and want to maximize your magazine capacity within legal limits, or simply prefer the feel and control of a slightly longer grip, the 3306 is a straightforward, durable solution.

Key Features

• Increases capacity by +3 rounds (9mm) or +4 rounds (.40 S&W)
• 6061 T6 aluminum billet construction for strength and durability
• Type 2 hardcoat anodize finish resists abrasion and corrosion
• Ergonomic shape and finger grooves for reliable magazine handling
• Torx screw retention system
• Designed and manufactured in the USA

Specifications

Frequently Asked Questions

Will the Warne 3306 extension fit my S&W M&P magazines?

Yes. The Warne 3306 is designed specifically for S&W M&P 9/40 magazines. It will add capacity to both 9mm Luger and .40 S&W versions of that platform.

How much capacity does this extension add?

The extension adds three rounds to 9mm Luger magazines and four rounds to .40 S&W magazines, making it useful if you need to increase your payload while staying within legal capacity limits in your area.

Is the extension durable for regular use?

Yes. The extension is machined from 6061 T6 aluminum billet and protected by Type 2 hardcoat anodize, which provides strong resistance to abrasion and corrosion. It's secured with a Torx head screw and washer for reliable retention.

Will I have trouble removing the magazine with this extension installed?

No. The extension features an ergonomic shape and finger grooves specifically designed to make magazine handling and stripping easier, even with the extension attached.