The best thing you can do to get started in the right direction with cast bullets is to measure your cylinder throats and slug your bore. You can then determine whether you’re likely to have luck getting lead bullets to shoot based on the bore and throat relationship. And if the throats are good to go it’ll tell you what size bullets you need to order.
If it interests you enough to do some reading on the subject Veral Smith’s book, “Jacketed performance with cast bullets” is a very informative and interesting read.
