If you make your own shot out of Bismuth and tin I doubt that there will be any problems with the USF&W Service. Once something is approved, that is good enough for the government. Bismuth shot was sold for reloading so they know that you can load your own shell with the approved shot. They would have to prove that you were making your own and that it did not measure up to specs. If you use only Bismuth and tin you should be safe as they have already approved it once. Just do not be stupid and mix in lead or just use straight lead and claim it is bismuth as one fellow I know tried.
I had Federal game wardens pickup wads in our field and claim that we were using lead shot at geese. To prove them wrong all I had to do was let them select one of my shells and open it for them to see that it had Bismuth shot and a regular wad, like the ones they had recovered, which could have been used for lead. I did offer them the bismuth shot so they could have it analyzed, but they declined.
