Before you send your gun anywhere, try wrapping a piece of copper scouring pad around a bore brush and use that to remove the lead fouling from your bore and cylinder throats. One solution to severe leading is to use gas check bullets rather than plain base. Leading mostly comes from the melting of the base of the bullet, the lead is then suspended in the propellant gasses and deposited along the barrel, this is why fouling is worse in the chamber throat, forcing cone and first part of the barrel than it is nearer the muzzle. Cutting a Taylor throat in the barrel might help, but I doubt that you need it, as the purpose is to improve accuracy by allowing the bullet to fully enter the barrel before it engages the rifling, rather than to decrease lead fouling. You could try using a smaller amount of faster powder, but this will not allow you to use the maximum power of the cartridge. Ensure that you bullet diameter matches the diameter of the chamber throat, as a loose bullet will foul from flame cutting if a seal is not made between the base of the bullet and the chamber walls. If the bullet is too hard, it will not expand under pressure to make a good barrel seal, if it is too soft, it is more prone to melting at the base, so choose the correct hardness for your application, softer for gallery loads and harder for full powered loads.