Preparing the receiver
If you have opted for a 100% complete receiver select either RIVET or SCREW build.
Bent blank with template
Whether your blank came with the template bonded on or you did it yourself you will want to measure all of the hole placements to ensure accuracy.
The correct hole placement is very important and I highly recommend that you check and remark any holes that are not perfect. To measure the placement go from the top of the rail to the center of the hole being sure to add the thickness of the receiver to the total. The correct measurements are as follows:
Safety selector .550"
Trigger pin 1.380"
Hammer pin 1.100"
Center support .750"
If your receiver is .040" thick you would add that to each measurement for the correct placement. Once you have all of the holes center punched you can drill them out. Drill the holes from each side, do not try to drill through as this may cause misalignment.
Hole diameters:
Right side Left side
Selector large .375" .200"
Selector small .200" None
Trigger .200" .276"
Hammer .200" .276"
Center support .200" .200"
You will need to drill the holes and cut the openings. To do this without damaging the blank you will need a mandrel. Cut a piece of wood 1.25" wide and 2" tall about 6" long. You will need to remove 1/2" wide by 1/4" deep section from both sides of the mandrel for proper fit.
Next insert the mandrel into the blank and use a center punch to mark each hole to ensure that the drill bit will not "Walk" off the mark. Drill the holes from each side. Do not try to drill straight through. The bit may "Wander" off center in the mandrel.
Once all of the holes are drilled you will need to cut out the larger openings with the Dremel or a mill. Be sure to make the cuts undersized and finish them with a file to ensure proper fit.
When all of the holes and cutouts are finished remove the template and you should have something that looks like this:
Go down to heat treating
Bendable flat
The first step is to lock the flat into the alignment bars of the jig. The flat will have two holes on the center line at each end. These will line up with the centering pins on the jig. The jig will also have a cutout to fit the mag well detent.
Tighten the bolts in series from the center out to ensure that the flat is held evenly. Use plenty of grease on the sides that will go down the inside of the frame. Place the flat on the bending frame with the bolts down and press the assembly into the frame. Use a 1" block between the jig and the press ram.
Start pumping the press and the receiver will start to form.
If you are using the jig from AK-Builder with the top rail attachment follow the directions you received with it. To form the top rails with all other jigs you will place the full assembly on your work bench and using a hammer start to tap the rails over. Do this slowly. Tap them over the a little at a time for the full length of the receiver.
Once you have them about 90% done use a piece of square bar stock as an anvil to finish. If you do the whole process with the hammer it will still work but will not look as good.
Reverse the jig and press the form out. Wipe off the excess grease.
Secure the receiver sides with a "C" clamp and remove the bottom bar. You will want to check the mag well edges and the left side trigger pin hole. Due to how close they are to the bend line they do not always set flat. A LIGHT tapping with the hammer will finish the forming.
Remove the receiver from the jig taking out the side screws. Lift out the center bar and then the side plates.
You should now have something that looks like this:
Heat treating
(If you are doing a screw build please refer to that section for more information)
To ensure a long life and proper function you will need to heat treat some spots on the receiver as well as the ejector. This can be easily done with a MAPP gas torch and a pail of water. BE VARY CAREFUL DURING THIS PROCESS! You will want to use gloves and probably move outside.
Heat treating the ejector
Holding the left lower rail in a pair of pliers heat ejector area to 1500 degrees as shown (Glowing yellow/orange) and then plunge it into the pail of water. Using a fine grain sand paper polish the treated area and re heat to 750 degrees as shown (Dull blue/gray). Let it air cool.
Heat treating the FCG holes
The FCG holes are the ones that the trigger and hammer pins go through. Each hole needs to be hardened and then annealed. To harden the holes heat each one to 1500 degrees as shown (Glowing yellow/orange) and then plunge it into the pail of water.
Do this with each of the four holes. Using a fine grain sand paper polish the treated areas to bare metal. Re heat all 4 holes to 750 degrees as shown (Dull blue/gray) and let them air cool.
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