C2300 is a high-leaded tin bronze, a bearing-grade casting alloy built around roughly 76-80% copper, 7-9% tin, and a substantial 13-17% lead. That lead content is well above what you'll find in ordinary bronze fittings, and it's the defining feature of the alloy: at this level, lead doesn't just help machinability, it turns the material into a genuine plain bearing alloy in its own right. Parts made from C2300 run directly against steel shafts without a separate bushing insert in many pump, gearbox, and industrial machinery applications.

The tin in the matrix gives the alloy the load-bearing strength and wear resistance expected of a bronze, while the dispersed lead particles provide a continuous supply of dry-film lubrication as the bearing surface wears in service, along with excellent embeddability for stray abrasive particles that would otherwise score a shaft. This combination makes C2300 a standard choice for bushings, thrust washers, wear plates, and slide bearings operating at moderate speeds and loads, particularly where oil-film lubrication can't always be guaranteed.

Few copper alloys machine as easily as high-leaded bronzes like C2300, and the reason is the same mechanism that makes the material a good bearing in the first place. The 13-17% lead exists as fine, soft particles scattered throughout the copper-tin matrix rather than dissolved into it. As the cutting edge advances, those particles smear and shear well ahead of the tool, breaking the chip into short segments and forming a thin lubricating film right at the cutting zone.

The practical benefits are lower cutting forces, reduced heat generation, minimal built-up edge, and chips that clear the cutting zone instead of packing around the insert or wrapping the workpiece. Surface finish is typically excellent straight off a general-purpose insert, and because the lead is soft rather than abrasive, tool wear stays low even at aggressive feed rates. The main things to watch for are the same as with any cast bronze: as-cast porosity, a harder outer skin from the sand mold, and the tendency of very high lead content to make thin sections and edges slightly more prone to tearing if the tool isn't sharp.

For reference, the benchmark for machinability among copper alloys is C36000 free-cutting brass at 100%. High-leaded cast bronzes like C2300 can approach or exceed that figure in some operations precisely because they carry even more lead by weight than free-cutting brass does.