You use copper jackets to prevent that. The big problem is one of sectional density, given 2 projectiles of equal size and shape but different weight the heavier projectile retains more energy, maintains velocity better and flies farther.
outofsalt : “Won’t steel bullets ream out the rifling on barrels a lot faster?”
SWAMPSNIPER : “You use copper jackets to prevent that....”
Bullet jacket material for much of US 30 cal rifle ammunition has been steel, with a thin copper plating, since the early 1950s at least. This includes 30M2 Ball and AP, and 7.62x51 NATO Ball M59 and M80. Go test some with a magnet.
Barrel wear rate differences between the plated steel and “gilding metal” (a specialized brass alloy, used in most jacketed applications in sporting ammunition since late 1920s) have never been disclosed. DoD numbers probably wouldn’t mean much to the civilian user anyway: other factors (bore size and finish, configuration of lands/grooves, projectile size and finish, propellant type, bore and projectile plating, dimensional differences from one manufacturer to the next, ambient conditions, and rate of fire) may dominate.
5.56x45 ball M193 has never been loaded with steel jackets.
Heavier projectiles enjoy the edge in energy only when muzzle velocity is equal. Given the limits on maximum chamber pressure, ammunition producers are often forced to provide lower velocities for heavier bullets, because they would otherwise exceed the pressure limits.
EPA is well-known in the outdoor/fishing/hunting products industry, for proposing bans on lead. Happens every few years; more likely to succeed each time.