The Bombay Stock Exchange benchmark Sensex tumbled by over 240 points in mid-session on Tuesday, after the Reserve Bank hiked inflation projection by this fiscal end in its second quarter monetary review. The 30-share Sensex, which commenced the day on a weak note as investors took to cautious trading, fell further to record a loss of 240 points at 16,500. With the selling pressure rising, the wide-based National Stock Exchange index Nifty fell below the crucial 4,900 level by losing 90.55 points at 4,880 a shortwhile ago.