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80% Lower Jig

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Showing all 3 results

80 Percent Lower Jig

The first step in building an 80% lower blank into a functional receiver is of course to buy one. Once that happens, you are still faced with the necessity of actually finishing it. To achieve this desired end state, you will need an 80% lower jig to properly guide you as you do the final mill work and hole drilling on your soon-to-be receiver.

The basic principle of the jig is that it is bolted securely to your receiver blank. With your receiver held firmly in place, the areas where you need to drill holes or remove metal are all automatically lined up where they need to be. At that point, all you need are the proper drill bits and end mills (which are specially designed drill bits that cut a squared-off end at the bottom of your hole rather than the conical end that regular drill bits create).

It is very important that you line up your receiver exactly as it needs to sit in the 80% lower jig and that you hold your drill exactly perpendicular to the sides of the receiver blank. If you allow it to wander up and down or right and left even a little bit, you will end up with an oval-shaped hole that will permit your retainer pins to walk out or, worse still; it will slightly misalign your parts, so they do not always function perfectly.

Both aluminium and composite receivers are made of fairly soft materials, so they cut very easily. Take your time. Check and recheck until you are certain that everything is good to go, then drill your holes slow and easy, nice and straight.