yup, they call the .54 "echo".
the patched round ball combo I use, creates a super-sonic speed. It's really not my fault, I simply spent the time finding the perfect combination for this gun. Proper ball size, patch thickness, the lube for the "cut at muzzle" with powder type and volume of charge.
many times the line judge will see the target being hit before they hear the sound of the powder charge. They get confused, they think they have heard an,,, / "The Echo".