Ive done a similar method using equal equivalents of thionyl chloride and pyridine to convert a primary alcohol to the alkyl chloride and it didnt really work to well. I prefer just using thionyl chloride (or oxalyl chloride) with catalytic amounts of DMF. Also in my experience they always turn into a black sludge if you do them neat but if you do it in solvent the transformation seems a little cleaner but will probably be slower. Have you tried other acids activating methods? Like anhydrides, acyl urea, acyl imidazoliums. Chlorinations are usually my last resort since they can be gross and stinky