When I wanted to load some bismuth loads for an old shotgun, and could not find any suitable loads I asked the big boys, they told me you can sub bismuth for lead, but you have to drop about an 8th oz less shot because of the weight difference, apparently bismuth acts more like a liquid just like lead does when fired from a shotgun, where steel acts like a solid, and that's what makes steel tricky.
TM
While well intentioned your ideas are not truly supported or adequately explained. Who are these “big boys” and what is the basis of their substitution?
You seem to state, reduce the lead shot load in the recipe by 1/8 ounce as a rule of thumb. Is that a 1oz load or 1 1/4 load etc.? The ratios may matter, though I have not seen this published anywhere on a reliable loading data website.
Are the lead loads you simply reduce the load by 1/8 at the top, middle, or low end of the allowable pressure spectrum? Your idea could be more or less dangerous depending on what lead load you choose to bastardize.
I know shot shell reloading can be forgiving and overbuilt guns can handle some abuse, but to throw out generalities without a basis in testing is dangerous. Many old SXS guns are capable of handling some big pressures, but many are not.
I have spent awhile tonight trying to find an authoritative source espousing your course of action but cannot.
There is sufficient tested data out there that owners of “an old shotgun” can find solutions with significantly lower risks than your course of action espouses.
