We report accurate temperature dependent measurements of optic indices of refraction, the birefringence, and the strain in the ferroelectric tungsten bronze crystals Ba0.25Sr0.75Nb2O6and two compositions of (Ba2−xSrx)2(K1−yNay)2(NbO3)10. These results are compared to our previous results in Ba0.4Sr0.6Nb2O6. From the experimental data, it appears that far above the ferroelectricTc, up to a temperatureTd, these crystals possess a local, randomly oriented polarization,Pd, with similarTdvalues, irrespective of their chemical composition andTc. Various aspects of our understanding of the polarization behavior and other effects in this ferroelectric system are discussed.