In this article, a novel simulation of the processing conditions of the anionic ring-opening polymerization of nylon 6 in a counterrotating twin-screw extruder by use of a modified Haake Rheometer run at elevated temperatures is described. Experimental results for several combinations of processing parameters are presented. General relations between processing parameters, conversion ratio, and molecular weight of the product are observed. These observations can be used in the eventual scaling up of investigations to an actual twin-screw extruder.