A witness handed the men on trial for killing Jam Master Jay an alternate theory of the crime Wednesday — telling the jury his nephew confessed to killing the Run-DMC icon because he reached for a gun. Raymond Bryant, the uncle of Jay Bryant, said his nephew made the admission at a relative’s house in Queens in 2003. And he was barred from speculating whether his nephew was working with accomplices. His turn on the stand was part of a lively day of testimony at the trial of Karl Jordan Jr. and Ronald “Tinard” Washington, who are accused of killing Jay, real name Jason Mizell, over a drug deal …