Acrylic copolymers produced via high-temperature solution polymerization are the base resin component for many automotive coatings. These polymers are often manufactured using a semibatch starved-feed reactor policy in order to tightly control copolymer composition and molecular weight. The combination of high temperature and low monomer concentration greatly promotes the importance of secondary reactions, causing observed conversion and molecular weight profiles to deviate significantly from those predicted by classic free radical kinetics. Although the effects of methacrylate depropagation and acrylate branching and scission have been studied during the homopolymerizations of butyl methacrylate and butyl acrylate, there is little knowledge as to how these mechanisms interact during copolymerization. In this work, we experimentally investigate the effect of monomer feed ratio on molecular weight and conversion profiles for high-temperature semibatch solution copolymerization of butyl methacrylate and butyl acrylate. A mechanistic model, constructed and implemented in Predici, provides a good fit to the experimental data set without any tuning of kinetic coefficients or other parameters.