Sylvan Arms GCB100 AR-15 to 9mm Conversion Block - Compatible with Glock 17 & 19 Magazines

The Sylvan Arms GCB100 AR-15 to 9mm conversion block transforms your standard mil-spec AR lower into a capable 9mm pistol caliber carbine—without buying a dedicated lower receiver. If you've already got an AR platform rifle and want to explore 9mm shooting for training, plinking, or general purpose use, this conversion block bridges that gap. Simply insert it into your rifle's magazine well, pair it with most 9mm AR uppers, and you're ready to shoot. It's a practical, cost-effective way to diversify your shooting without a major investment.

The GCB100 is designed to accept Glock 17 and Glock 19 magazines, which means you can leverage affordable, widely available factory mags and even share ammunition supply with other pistol-caliber platforms in your collection. The magazine release uses a trigger-style lever that lets you drop a magazine one-handed—a thoughtful detail that improves handling and speed at the bench or on the range. Built from aircraft-grade 6061 aluminum, it's engineered to handle repeated use without compromising fit or function.

This is a smart addition to your AR setup if you want the flexibility of 9mm without the complexity or cost of a full second build. Whether you're looking to shoot cheaper rounds, reduce recoil for training, or just add versatility to your lower receiver, the Sylvan Arms conversion block delivers a straightforward, reliable solution.

Key Features

• Converts standard mil-spec AR lower to 9mm pistol caliber carbine
• Compatible with Glock 17 and Glock 19 magazines
• Trigger-style magazine release for one-handed operation
• Aircraft-grade 6061 aluminum construction
• Works with most 9mm AR uppers

Specifications

Frequently Asked Questions

Will the Sylvan Arms 9mm conversion block work with my existing AR lower?

Yes, the GCB100 is designed to fit standard mil-spec AR lowers. You insert the conversion block into the magazine well of your existing lower, then pair it with a 9mm AR upper to create a functioning pistol caliber carbine.

What magazines does this conversion block accept?

The GCB100 is compatible with Glock 17 and Glock 19 magazines, giving you access to affordable, commonly available factory magazines.

Can I use this conversion block with any 9mm AR upper?

The GCB100 works with most 9mm AR uppers. We recommend confirming compatibility with your specific upper before purchase to ensure proper fit and function.

Is the magazine release easy to operate?

Yes. The trigger-style magazine release is designed for one-handed magazine removal, improving speed and ergonomics during shooting or handling.