Just curious as to why anyone would want to do this? As a steel ball of a given size will weigh less than a lead ball of the same size it will have less striking power and loose momentum faster than a lead ball. I would also want a looser fit with a steel ball as there would probably be a little ‘give’ with lead and none with steal. Don’t know but it sounds like something I personally wouldn’t want to do and perhaps a good way to ruin a gun and also maybe your day. Just my guess though.
RJ
