Leading is the deposition of significant amounts of bullet metal on the bore. It can take many forms -- streaks, chunks, splotches, films, etc. (more on this in a minute). It's important to recognize that the mere presence of streaks in the bore is not an indication of leading; many types of bullet lube (especially the commercial hard lubes) leave perfectly innocuous streaks in the barrel that have no negative impact on firearm performance (if a wet patch removes the deposit, it probably wasn't lead). Nor is a gray "haze" on the bore surface necessarily a problem; it can be an indication of a leading problem, but it can also be simply a reflection of the alloy of barrel steel used, how the rifling was cut, or a reflection that the barrel isn't "broken in" yet. The inexperienced cast bullet shooter commonly (and falsely) believes that leading has but a single cause -- the bullet was too soft for the velocity, and lead was stripped off the bullet as it raced down the bore. To this novice shooter, the only solution to leading is to cast the bullet harder, which may solve the problem, but in many cases it won't (and in certain cases it will actually make the leading worse). If the harder bullets don't solve his leading problem, the novice generally walks away thinking that it's impossible to shoot cast bullets without leading a barrel, when in fact the real problem is simply one of misdiagnosis. So let's look at some of the firearm and ammunition issues involved in leading ...
