Here is how I would make a receiver wrench: Actually, I would make 2, because the process produces an extra part.
Cut 2 pieces of 1" or larger square barstock about 5" long. Clamp them together in the 4 jaw chuck, centred where the 2 pieces come together. Drill and bore a hole through (1/2 hole in each) slightly larger in diameter than the receiver ring of the rifle. Extra space is for a brass or aluminum shim to prevent marking. Cut one or two pieces, same stock, about 10" long, drill a hole for the lug on the bottom of the receiver to drop into offset about 1/3 of the way along the bar. Centre drill the ends, turn one end round for about 4 or 5", to fit inside a pipe handle. Align the 1/2 hole in the one piece with the lug clearance hole in the second piece. Drill a couple of holes through both, threading the holes in one piece, clearance holes in the other; 1/2" x13 bolts will work for clamping the pieces together on the receiver ring.
To use, place a shim over the receiver ring, one piece wraps around the receiver ring, the second part goes against the bottom flat on the receiver, with the lug protected in its hole. Clamp tight with the two 1/2" bolts. Clamp the barrel in barrel vice, apply pipe handle to the receiver wrench, have at it.
With the right sized half hole, and turned split bushing halves of the correct diameters, the wrench will work on any round top, flat bottom receiver. Reverse the half holed piece, flat to flat, and the wrench will grab flat receivers, like a 94 Winchester. Use longer clamping screws, and it will work on a M-1/M-14.