you actually need about 3 or 4 bucking bars. one for the 4 rivets in the bbl. hole of the trunnion. one for the rearmost bbl. trunnion holes. one for the rear trunnion's rivets (mine is double ended) and one simple bar for the trigger guard...which i sometime skip and use a thinned rivet setting punch against a steel plate.
no pics that i know of, but if you ask mg34ss, he may send you a pic of his unique "cam bar" that he uses for the front trunnion's bbl. area rivets.