The incident happened early Saturday at the couple's home in Delaware County, the Philadelphia Daily News reported.
Michele Wanko, 42, told police she and her husband, William Wanko, 43, had been drinking for about six hours when she asked him to show her how to use a gun.
Police said William Wanko then pulled out several weapons from a safe in the couple's basement and showed his wife how to use them properly.
Then, as William Wanko was pulling another gun out of the safe, Michele Wanko picked up a semiautomatic pistol, pulled the slide back as her husband showed her and the gun went off, striking William Wanko in the throat.
"He was able to say, according to her, 'I can't believe you shot me,'" said Parkside Borough Chief John Egan.
Michele Wanko was charged with involuntary manslaughter and related offenses.
"It's a very sad situation, not only for the wife who has to live with this for the rest of her life, but their children who have to live with this and, of course, have to grow up without a father," Egan said.