The BSE benchmark Sensex has gained over 320 points in opening trade today.The 30-share index, which has lost 827.41 points over the course of a five-session losing streak, recovered by 320.10 points, or 2.10 per cent, to 15,495.18 in opening trade amid a rally in financial, realty, metal, auto and capital goods stocks.In a similar fashion, the wide-based National Stock Exchange Nifty index gained 97.10 points, or 2.13 per cent, to 4,641.30.