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80 Lower Jig Spotlight: Router Jig Extreme Multi-Platform by Modulus Arms (AR-15 / AR-9 / LR-308)

A new challenger has entered the 80 Lower Jig Spotlight ring: The Router Jig Extreme Multi-Platform by Modulus Arms! This beautifully red-anodized 80 lower jig is compatible with all 80% lowers, including AR-15, AR-9, and LR-308! But is it good enough to beat out the crowd favorites like the Easy Jig Gen 2 and the 5D Tactical?

Let’s find out:

Modulus Arms Router Jig Extreme at a glance

Modulus Arms claims the Router Jig Extreme’s breadwinner comes in the form of its speed: With a reported machining time of fewer than 15 minutes, this would indeed make the Router Jig Extreme faster than any other 80 lower jig available.

The Modulus Arms Router Jig Extreme’s speed also comes with plenty of cool features that help make sure you’re not making mistakes (or ruining your shiny, new 80% lower) while you’re blazing along.

A proprietary, one-piece guide pin system guides as you trace the fire control group pocket profile guides, ensuring your end mill bit never touches the jig. This virtually eliminates tool-on-tool contact, extending the life of the Router Jig Extreme.

The Router Jig Extreme also has plenty of other features that we’ve come to expect from a top-tier 80% lower jig:

  •         Swaps between AR-15, AR-9, and LR-308 in seconds
  •         All wear surfaces machined from hardened steel plates
  •         1.5”-thick no-touch side plates ensure drill bits remain stable while using hand drill (That means no need for a drill press!)
  •         Requires only one pilot hole for end mill bit
  •         Integrated depth gauges allow for easy end mill bit setup
  •         Integrated shop vac attachment provides easy clean-up of debris while working

We’re particularly fond of the no-touch plates. The largest barrier of entry to building an AR with an 80% lower is the need for a drill press – a large, commercial piece of equipment most of us simply don’t have access to.

Router Jig Extreme SpeedMILL End Mill System

But the Router Jig Extreme’s most popular feature may be its patented SpeedMILL end mill bit. Modulus Arms developed their own 80% lower end mill bit to accommodate the most popular handheld routers you might use. More importantly, the SpeedMILL system was developed specifically with 80% lower work in mind.

The bit’s steel coupler is heat-treated, causing it to expand to accept 5.16” solid carbide end mills, which are specifically designed for 80% lower jigs. The end mill is also thermal fit so it’ll never slip or vibrate, resulting in cleaner, quicker cuts. The bit is also reduced to just 1.5” in length, increasing rigidity for a mirror finish.

Modulus Arms Router Jig Extreme: Final verdict

The Modulus Arms Router Jig Extreme appears to be the next hottest 80% lower jig by our measure, and for good reason. The SpeedMILL system truly captures the heart of what makes this project feasible, even easy: Providing quality, easy-to-use tooling that makes this project safe and easy for beginners.

The Router Jig Extreme will require you to purchase the right SpeedMILL system, which will only be compatible with the handheld router your purchase (or may already own). The Router Jig Extreme is also slightly more expensive than competitors, though we feel its speed and ease of use are certainly worth it.


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