CMMG 57AFD1E 5.7x28mm Extension - Compatible with FN Gen1 Five-seveN Magazines

The CMMG 57AFD1E 5.7x28mm extension is a magazine capacity upgrade designed for shooters running FN Gen1 Five-seveN magazines. If you've got an early-generation Five-seveN and want to carry or store more rounds without swapping mags, this extension adds 10 rounds to your existing magazine tube. It's a straightforward way to boost capacity on compatible Gen1 magazines—just slide it on and you're done.

The 5.7x28mm cartridge has carved out a niche for shooters who value compact, low-recoil performance with decent velocity and magazine capacity. Whether you're running the Five-seveN for sport shooting, duty applications, or general range work, magazine real estate matters. This CMMG extension lets you get more rounds downrange between reloads.

One thing to lock in: this extension is built specifically for FN Gen1 Five-seveN magazines. The newer generation magazines are not compatible, so verify what you're working with before ordering. If you're running original-generation Five-seveN mags, this is a proven way to add capacity without hunting down harder-to-find magazine options.

Key Features

• Adds 10 rounds to compatible FN Gen1 Five-seveN magazines
• Designed and manufactured by CMMG for reliable fit
• Works only with FN Gen1 magazine tubes—verify compatibility before purchase

Frequently Asked Questions

Is this extension compatible with newer FN Five-seveN magazines?

No. This CMMG extension is designed exclusively for FN Gen1 Five-seveN magazines. It is not compatible with the newest generation magazines, so check your magazine to confirm it's a Gen1 before ordering.

How many additional rounds does this add?

The extension adds 10 rounds to your existing FN Gen1 magazine tube.

What's required for installation?

The product details provided do not include installation instructions or tools required. Contact CMMG or the retailer for assembly guidance if you need it.