SYLVAN ARMS COVERSION BLOCK AR15 9MM SIG P320

The Sylvan Arms Conversion Block for AR15 9mm is a drop-in adapter that lets you run SIG P320 magazines through your standard Mil-Spec AR-15 lower receiver without swapping to a dedicated pistol-caliber platform. If you already own an AR-15 lower and want to add a 9mm capability for plinking, competition, or training without the expense of a second lower, this conversion block bridges that gap with straightforward installation and real versatility.

The design installs directly into your existing lower receiver—no gunsmithing required. Once installed, it accepts SIG P320 9mm magazines and functions like a standard magazine feed system, making the transition intuitive if you're already familiar with AR ergonomics. You'll need a 9mm upper receiver to complete the build, but the lower stays in your safe doing double duty. It's the kind of practical solution that appeals to shooters who want to stretch their existing inventory and explore a new caliber without the commitment of a full second rifle.

Built from steel and 6061-T6 aluminum with a black anodized finish, the conversion block is engineered for the long haul. At 4.2 ounces, it adds minimal weight to your lower. One trade-off worth noting: this block does not provide last-round bolt hold-open functionality, so you won't get that audible or tactile confirmation when the magazine runs dry. That's a fair trade for the simplicity and cost savings, but it's worth knowing before you buy.

Key Features

• Drop-in design fits Mil-Spec AR-15 lower receivers with no modifications
• Compatible with SIG P320 9mm magazines
• Steel and aluminum construction with black anodized finish for durability
• Simple installation and quick magazine swaps
• Lightweight at 4.2 ounces

Specifications

Frequently Asked Questions

Will this conversion block work with my standard AR-15 lower?

Yes, the Sylvan Arms conversion block is designed to fit directly into Mil-Spec AR-15 lower receivers. It installs as a drop-in component with no gunsmithing or modifications required.

What upper receiver do I need to use with this conversion block?

You will need a 9mm upper receiver to complete your build. The conversion block adapts the lower to accept SIG P320 magazines, but the upper must be chambered in 9mm and compatible with your lower receiver setup.

Does this block support last-round bolt hold-open?

No. The conversion block does not include last-round bolt hold-open functionality, so the bolt will not lock back when the magazine is empty.

What magazines does this conversion block use?

The Sylvan Arms conversion block is compatible with SIG P320 9mm magazines.