The BSE Sensex gained over 250 points, to trade at 16,777 in the afternoon session. Earlier, the 30-share index, which lost nearly 21 points in the previous session, shot up by 162 points, to around 16,699 in the first five minutes of trade today, with IT, tech, metal and banking sector stocks leading the rise.Similarly, the broad-based NSE Nifty rose by nearly 75 points, to 5,049.