MCA Music Entertainment Group yesterday announced that MCA Records posted its best monthly sales total ever in September.The company claimed it grossed more than $ 50 million in sales. Releases by Bobby Brown, Mary J. Blige, Vince Gill, Elton John and Jodeci, among others, were cited by the company as the reason for the prime September. Al Teller, chairman of MCA Music Entertainment Group, praised his division presidents and noted that the sales were achieved with both veteran and developing artists. MCA also is looking toward a strong fourth quarter, with releases expected from Bell Biv DeVoe, Trixter, Stephanie Mills, Patti LaBelle and George Jones, as well as a B.B. King boxed set.