A chopper assembly for a crop residue distribution system of an agricultural combine may include a rotor shaft extending lengthwise along a rotational axis between a first end and a second end. The chopper assembly may also include a plurality of flail blades pivotally coupled to the rotor shaft. Each flail blade may be configured to pivot relative to the rotor shaft about a pivot axis, with the flail blades being spaced apart axially from one another between the first and second ends of the rotor shaft. In addition, the chopper assembly may include one or more features configured to improve the performance of the chopper assembly during low speed operation. For example, the feature(s) may correspond to one or more fixed blades coupled to the rotor shaft and/or one or more torsional springs provided in operative association with one or more of the flail blades.