This tool is the front trunnion rivet locater. Using a piece of .040" scrap fold it into the shape shown below. Once folded drill a .156" hole as shown. You will want to shorten the rivet shank to .250" and solder it to the hole in the short arm.
Once the front trunnion is in the 80% receiver the rivet holes will be covered. This little gem will let you accurately place the front rivet holes without a lot of hassle or "Egging" of the holes to get them to align. When you insert the short arm into the trunnion position the rivet in the hole and the outside hole will be perfectly lined up.
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