I have experience shooting five tc 50 cal barrels and all shot very well with .018 patching. Ticking or preferably #40 drill with .495 ball. And yes, I could feel differences in how tight was the fit. They all required a rap to start them. Once started they all slid easily enough down the bore. So, I don't understand why some have difficulty starting and loading that combo.
Same result with 45, 54 and 58 bores. Some TC, some Spanish, some Italian and some American. The only barrel that it hasn't worked with is an FIE pistol that is marked 45 caliber but is actually a 44. With a .433 ball it falls in line.
Some highly accomplished competitive shooters shoot the same patching with bore diameter balls.