This work is concerned with modeling the free-radical high-pressure copolymerization of ethylene and vinyl acetate. Hereby, the focus lies on developing a kinetic model that depicts the molar mass distribution, especially for high molar masses and long-chain branching across various conditions, including different vinyl acetate content, temperatures, conversions, and reactor types (mini-plant and industrial scale). The approaches were deriving new kinetic coefficients from published data, using a high-temperature refractometer to measure refractive index increments for precise molecular weight distribution analysis, and synthesizing a diverse set of copolymer samples for comprehensive validation of the kinetic model.