The Sensex at the Bombay Stock Exchange ended with a modest gain of 31 points, or 0.2 percent, at 16,183, amid firm Asian and European markets, today. The Nifty at the National Stock Exchange rose 15 points, or 0.3 percent, to 4,906.Stock markets in Japan, China, South Korea and Singapore gained between 0.2 percent and 0.9 percent.