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Secrets You Should Know Before Finishing an 80 Lower

Machining an 80 lower into a finished AR-15 lower receiver can be a surprisingly easy, fun, and enjoyable experience – or it could be a disaster, a waste of time, and a sunk cost. Let’s short for the former! Here are some secrets and tips you should know before you even add an 80 lower jig or router to that shopping cart:

  1.    Start with a billet 80% lower

Sure, a forged, mil-spec 7075 T6 lower that’s hard as Hell and ready for war is cool, but it’s also more difficult to machine than a billet 6061 T6 lower. You’ll want to work with a more forgiving alloy that makes the machining process easier. After all, you’re learning as you go. Don’t make it harder than it needs to be.

  1.    Watch the tutorial, read the instructions first

Machining an 80% lower can sound confusing and it certainly looks difficult, especially if you don’t know what’s happening. Do yourself a favor and watch some of our video tutorials that walk you through the entire process.

Don’t watch these for the first time while you’re attempting to machine your first lower! That’s like commuting in L.A. while getting your learner’s permit. Trust us, take that one, whole hour out of your day to just watch, read, and listen. You’ll be thankful to yourself for understanding the process and seeing “the big picture” before you actually turn on that router and start spinning that end mill bit.

  1.    Buy a quality 80 lower jig, tooling, and router

You will be operating a machine that spins at tens of thousands of revolutions per minute. Attached to that spinning device will be a sharp, metal tip. That metal tip will be throwing raw chunks of metal everywhere. You want quality equipment for this.

Invest in a top-rated 80 lower jig like the 5D Tactical PRO or the Easy Jig Gen 2. We also recommend sticking with our tried n’ true Porter-Cable hand router and the appropriate 5D Tactical or Easy Jig tooling.

  1.    Measure twice, and take breaks

Machining an 80 lower is a process that requires careful concentration and a steady hand. Usually, you can machine a lower in less than two hours. While that might not sound like a lot of time, it can be mentally and physically taxing. Take breaks during the process.

Also measure your depths and double-check your router and jig setup during the machining process. Never move your lower once it’s seated in the jig, and take your time de-burring rough edges and cleaning out your work area of debris.

Taking small breaks with a coffee or beer, keeping your area clean, and generally admiring your work as you go will help to ensure you’re not rushing or getting frustrated and tired. After all, this is a firearm you’re building – you need precision and patience.

  1.    Have your lower parts kit handy, test-fit!

Of course our 80% lower jigs are quality machines and they ensure you’re machining precisely, but it’s always a good practice to have your AR15 lower parts kit handy so you can test-fit everything in the fire control group area. Even a couple thousandths of an inch can make the difference between a reliable shooter and an aluminum paperweight.

Plus, once you have your lower parts kit, you can keep on building once you’ve finished machining. Now it’s time to get to work! Check out our 80% lower-and-jig bundle kits, and be sure to browse through our mil-spec, affordable lower parts kits.


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