Propagation rate coefficients, k(p), with confidence ellipses of the Arrhenius parameters, are reported for bulk free-radical homopolymerizations of n-butyl and n-dodecyl methacrylate at ambient pressure and low conversion. The data which are from independent experiments in two laboratories, were obtained by the pulsed-laser polymerization / size-exclusion chromatography method. They obey the consistency criteria established for this technique. Plotting the n-butyl and n-dodecyl methacrylate k(p) data together with the benchmark k(p) values for methyl methacrylate and recent data for four other linear and branched alkyl methacrylates clearly shows a pronounced family-type behaviour of alkyl methacrylate k(p).