A model of free-radical cross-linking copolymerization in solution, based on Flory's gelation theory and developed by Tobita and Hamielec [Macromolecules 1989, 22, 3098-3105] has been applied to the system acrylamide/N,N'-methylenebisacrylamide. The evaluation of missing rate constants was performed by comparing model predictions with experimental measurements of swelling ratios and literature data. This way, the interplay of cross-linking and intramolecular cyclization reactions, regulating the network formation and its properties, has been deepened. It turns out that the primary intramolecular cyclization is practically independent of the cross-linker amount employed, but it is affected by the total monomer concentration. For the latter dependency, an empirical correlation was proposed, which was tested in parametric simulations, showing its impact on the properties of hydrogels.