Earl Coleman was pulled over Jan. 30 in Kalamazoo County. Police initially found a small amount of heroin hidden in his shoe.
Following his arrest, they said they located the 10 grams in his butt and then obtained a warrant to search his home.
In addition to 85 grams of heroin, they also found a loaded semiautomatic handgun underneath his bed.
Coleman is charged with possession with intent to distribute and felony firearms.
Because of having multiple felony convictions in Michigan, police said his right to possess firearms was not restored.
In a release from U.S. District Court, officials say that Coleman admitted to selling heroin since the summer of 2013.