G80 Receiver Build Instructions [Polymer Jig]

If the jig arrived assembled on a receiver, pull the two bodies off the receiver first. Lay out every piece from the list above so you can see it before you start cutting.

1. Seat the receiver in one jig body.
2. Insert the steel dowel pins into the receiver’s pre-drilled holes.
3. Mate the other jig body to the receiver so the two halves close around it.
4. Drop the hex nuts into the slots on the nut-slot side.
5. Run the three #8-32 screws through the jig and into those nuts. Tighten with the Allen key until both bodies sit flush.

1. Swap the factory collet in your rotary tool for the 3mm collet from the kit.
2. Insert the grinding drum. Leave about 1/4 to 1/2 inch of shank exposed past the end of the collet.
3. Tighten the collet until the drum will not walk out under load.

Eye and ear protection on. Set the rotary tool to its high speed setting.

1. Turn the tool on and move it slowly back and forth over the top of one rail blocking tab.
2. Take the tab down until it is nearly flush with the rails.
3. Finish with light passes until the surface is flush. A bare finger run across the rails should not feel a protrusion where the tab was.
4. Repeat on the other three rail blocking tabs.

1. Keep the grinding drum. Approach the tab from its left side and keep the tool off the right wall of the receiver.
2. Take the bulk of the tab down with the drum.
3. When little material remains, switch to the grinding cone.
4. Bring the surface flush to the left wall with the cone.

This tab is the U-shape at the front of the receiver.

1. Switch back to the grinding drum for the bulk of the material.
2. Approach from the top of the U and work down toward the bottom of the receiver. A light front-to-back motion brings the tab down.
3. Near the bottom, switch to the grinding cone and take the surface flush.

The bushings are marked on the jig. Use the bit that matches the marking. Do the #21 holes first, then the #31 holes.

1. Install the #21 bit. Seat the smooth shank deep in the chuck. Do not put any of the cutting flutes in the chuck.
2. Tighten the chuck until the bit will not walk. Set the drill to a medium torque setting. Keep lubricant next to the jig.
3. Set the jig with one side facing up. Put the bit in the #21 bushing. Add a few drops of lubricant.
4. Turn the drill on and apply light to moderate pressure. If you see smoke or hear the bit squeal, stop and add lubricant.
5. When the bit drops through the completed hole, stop. Reverse the drill and run it to back the bit out. That also clears burrs.
6. Flip the jig and repeat in the #21 bushing on the other side.
7. Remove the #21 bit and install the #31 bit the same way: shank only, chuck tight.
8. Lubricate the #31 bushing and drill it the same way, light vertical pressure, until the bit falls through. Reverse to extract.
9. Flip the jig and finish the last #31 hole.

1. Use the Allen key to remove the three screws. Take one screw all the way out before you start the next.
2. Wiggle the left and right jig bodies apart.
3. The receiver should drop free. The dowel pins may come out with the receiver instead of staying in the jig. If they do, pull them out of the receiver.

1. Wipe the receiver down with a rag and some lubricant. Use fine grit sandpaper on any burrs left by drilling.
2. Test fit the slide without the barrel and recoil spring. The slide should run freely over the rails.
3. If you feel drag, set the receiver upside down on the sandpaper and move it in a circle to knock down remaining burrs. Test the slide again. It should travel fully to the rear and return to battery.
4. Install the barrel and recoil spring in the slide and repeat the test. The recoil spring must fully compress and expand without catching. That confirms the recoil spring channel is clear.