FMJ bullets do not produce leading. Most lead bullets do leave lead in barrels. Unless you reload, and you want to avoid leading, go with FMJ or JHP projectiles.
Clarification here; jacketed bullets generally cause no leading deposits but can (and regularly do) leave varying degrees of fouling by transferring of the jacketing material to the lands and grooves, and this can be especially difficult to remove with routine cleaning methods. Bullet jackets are usually made of copper alloys ranging from pure copper to bronze (copper-tin alloy) or brass (copper-zinc alloy). Some manufacturers utilize aluminum alloys or mild steel, sometimes with a light plating of copper alloy, sometimes with a coating of lacquer (with or without coloring added).
Wear and tear on the firearm and bore surfaces are one factor to keep in mind, but very few recreational shooters will ever fire enough ammo to "shoot out" the bore of any firearm. Residual deposits of bullet jacket metal can require much more effort to remove than any amount of leading deposit, and the resulting wear and tear can be far more serious than recreational shooting is likely to cause.
There are solvents specifically formulated to help remove copper fouling (the most common bullet jacketing material), when used in compliance with the maker's instructions (usually specifying application methods, working time, and removal methods). There are also some solvents that can be corrosive, particularly to parts made of aluminum alloys, or to certain types of finishes (such as nickel plating).
Leading deposits from cast or swaged lead alloy bullets can be a chore, but removal methods are really straightforward. The lead alloys are all much softer than barrel steel and much softer than good bronze bore brushes, so removal is simply a matter of repetitive brushing to remove the leading deposits and return to bare steel in the bore, chambers, forcing cones, etc.
Individual firearms, regardless of manufacturer or reputation, may display measurable differences in dimensional tolerances. SAAMI nominal specifications may call for .357" jacketed or .358" lead-alloy bullets, but very well known and respected revolvers may have chamber throats, forcing cones, bore and groove diameters that vary considerably in manufacturing tolerances. A standard rifled bore might be .350" with .358" rifling groove diameters, but a variance of several thousands of an inch is pretty common in production pieces. The drills, cutters, and reamers used in production are expensive precision tools that remain in use over the course of several thousand applications, starting out slightly larger and remaining in use until worn down in use to below the manufacturer's tolerances (and those tolerances will vary from one company to another).
There is only one real commonality, and that is the fact that every firearm will require cleaning after use.
