How do you reduce a AGW #1 wire to fit in a circuit breaker that will only go up to #4 AGW?

Using a sharp pointed pair of wire snips/cutters, cut two or three stands out of the wire and re-arrange the remaining wires with a pair of pliers in order to make it fit into the lug. Careful to ONLY remove as many strands as necessary to fit snug into the lug. ...(OH! you'll have a "snug lug"!) :-)