Choosing an 80% Lower and Jig Kit
A jig kit takes the guesswork out of finishing a lower — the jig holds the receiver and guides your drilling and milling. A few things to decide before you pick one.
What's in the kit
Each kit includes an 80% lower receiver and a jig to guide the milling of the fire-control pocket, trigger slot, and pin holes. You supply the tools (drill press or router and bits) to do the work. The kit does not include a lower parts kit or any upper components — those come after the lower is finished.
Polymer vs. aluminum
Polymer lowers are lighter and easier (and cheaper) to mill with basic tools, which makes them a forgiving first build. Forged or billet aluminum lowers are stronger and closer to a standard production receiver, but take more care and better tooling to finish. We stock both — choose based on your tools and how much margin for error you want.
AR-15 vs. AR-10 / .308
Most kits here are AR-15. We also stock a .308 / AR-10 lower-and-jig system for large-frame builds. AR-15 and AR-10 lowers are not interchangeable, and large-frame patterns differ, so match the kit to your platform — check the .308 product page for its pattern compatibility before pairing it with an upper.
Single, 2-pack, or bulk
Buying more than one lower? The 2-pack and bulk 5-pack sets bring down the per-lower cost and include a jig for the set — a single jig finishes multiple lowers of the same pattern, so you don't need one per receiver.
Using the jig
The jig clamps around the 80% lower and provides the drill and mill guides for the trigger pocket and pin holes. Work slowly, follow the depth marks, and the jig keeps the cuts aligned. It's reusable, so it carries over to your next lower of the same pattern.
Frequently Asked Questions
What's included in an 80% lower with jig kit?
An 80% lower receiver and a jig that guides the milling of the fire-control pocket and pin holes. You supply the drilling/milling tools. It does not include a lower parts kit or upper.
Is the jig reusable?
Yes. A jig can be used to finish multiple lowers of the same pattern, which is why the 2-pack and bulk 5-pack sets include just one jig for the whole set. Keep it and it carries over to your next compatible lower.
Should I get a polymer or aluminum lower for my first build?
Polymer is lighter, cheaper, and more forgiving to mill with basic tools, so it's a common first choice. Aluminum (forged or billet) is stronger and closer to a production receiver but demands better tooling and more care. Match it to the tools you have.
Will an AR-15 jig work for the .308 / AR-10 lower?
No. AR-15 and AR-10/.308 lowers are different sizes and patterns, so each needs its jig matched to that receiver. The .308 kit ships with the correct jig for that lower.
Do you need an FFL to buy an 80% lower with jig?
This is the specific case to watch. Following the 2025 U.S. Supreme Court decision Bondi v. VanDerStok, ATF can treat certain unfinished receivers sold as a kit with a jig and the parts needed to readily complete them as firearms — meaning serialization and transfer through a licensed dealer (FFL). How a given kit is regulated depends on exactly what it includes and where you live, and state laws vary. Confirm the current federal requirement and how a specific kit ships before ordering. This page is general information, not legal advice — review it against current law.
