In the .577, you could easily use a .570 swaged or cast ball and it would be esier getting it started. As long as the ball and patch is started whtout cutin the patch, you're home free. Oh yeah, it has to be a tight combination to work well. About anything will work after a fashion. In 75, there was a guy at the Barnet range shooting a .50 Ietie gun. To me, he excitedly exclaimed, "Some people just throw these away, I shoot them". He was filing the rims down a bit on once fired .30/30's, filling them with sand then plugging them with wax. He even hit his 25 yard target, sometimes - pretty excited when he did - (another exclamation) - "These things re pretty accurate".