300M & 4340M Alloy Steel is a chrome nickel moly alloy and a modified 4340. The addition of vanadium and higher silicon content is added to produce higher strength levels. 300M offers an excellent combination of toughness and torque at high strength levels. It also has high fatigue, transverse ductility, toughness and creep characteristics. VAR (CEVM) Consumable Electrode Vacuum Melted. E4340 Modified – 300M – 4340MOD.