Carlson’s 04521 Magazine Extension, 12 Gauge, Remington Fit

This Carlson’s 04521 magazine extension is designed for use with Remington 870, 1100, 11-87, Versa Max, and V3 shotguns chambered in 12 gauge. Constructed of blued solid steel, the extension replaces the factory magazine cap to provide an expanded magazine length. Hardware included with the extension consists of a spring and a base clamp with swivel stud; a quick-detachable swivel is not included. Some extensions ship with a high-visibility follower, while others require the factory follower to function.

Key Specifications

• Compatible with Remington 870, 1100, 11-87, Versa Max, and V3 shotgun models.
• Designed for 12 gauge shotguns.
• Manufacturer part/model number: 04521.
• Construction material is blued solid steel for corrosion resistance and durability.
• Includes a spring and a base clamp with swivel stud for attaching a detachable sling swivel.
• Some units include a high-visibility follower; others require the factory follower to be used.
• The threaded tube replaces the factory magazine cap to extend magazine length.
• Intended use cases include home protection, competition shooting, and law enforcement applications.

This magazine extension offers a practical way to increase magazine length and streamline reloads for compatible 12-gauge Remington shotguns. Its blued steel construction and included mounting hardware make it a durable, straightforward upgrade for shooters focused on reliability and function in competitive, range, or defensive contexts.