I recall an article in a Gun Digest years ago by Roger Barlow titled, if my memory is anywhere close to correct, Square Shot & little Flying Saucers. He reported on making both homemade cube & disc shot. He did this for the cube shot by pouring a lead sheet & then cutting it into cubes & for the disc shot by placing regular shot between steel plates & pressing them into discs. As best I recall his results proved to be acceptable for a short range spreader load but would be considerable work if more than a very few shells were needed of this type.
