  We use our synthetic Horizontal Branch (HB) procedure to approach the debated
problem concerning the adequacy of canonical HB stellar models to account for
the observed peaked distribution of RR Lyrae fundamentalised periods in the
globular cluster M3. We find that by assuming a suitable bimodal mass
distribution, canonical models account for the observed period distribution. In
particular, the best fit model, out of nine random extractions, reaches a 99.9%
Kolmogorov-Smirnov (KS) probability. We also attempt a prediction of the
relative distribution of variables in fundamental and first overtone pulsators,
reaching a rather satisfactory agreement. However, one finds that canonical
models outnumber by roughly a factor of two the observed number of red HB
stars. Possible solutions for this discrepancy are outlined. Alternative
evolutionary scenarios are also briefly discussed.
