You will probably detect an astringent harshness when you taste a gravity sample. There could be other factors that influence extracting tannins from your grain husks. If you used/have hard water, for instance, if your steeping grains were lighter in color, if you used an excess volume of water for steeping, if you steeped for a long time, etc. If, however, you steeped some darker grains and steeped in about 1- 1 1/2 quarts of water per pound of grain, the pH of the steeping liquor would be low enough that tannin extraction would probably not be an issue at 170.