MANISTIQUE, Mich. (AP) _ A man armed with a .44-caliber Magnum, a deer rifle and a double-barrel shotgun barricaded himself inside a drug store, where he downed 21/2 pints of peppermint schnapps and passed out, officials said today.

After a one-hour standoff Monday, police in this Upper Peninsula community found the 24-year-old man sitting unconscious behind a counter at Putvin Drug Store, a revolver in his lap and a knapsack full of ammunition nearby, said public safety director James St. Louis.

The man allegedly asked to see a revolver at a sporting goods store, loaded it and held up the store, grabbing more guns and ammunition, police said. He crossed the street to Putvin's, pointed a gun, ordered everyone out and set a cannister of gunpowder on a chair, threatening to shoot it, police said.

St. Louis said he telephoned the gunman, who, at first, was coherent.

''Then, about a half hour later, his speech became slurred and he began to ramble. He had begun drinking schnapps which the store sells,'' St. Louis said.

The gunman's mother and sister said he passes out quickly when drunk, so police waited.

''About an hour after the incident began, we heard the phone fall to the floor and we could get no further response from him,'' said St. Louis, who entered the store with two officers and apprehended the sleeping man.

The man's name was withheld pending arraignment Thursday for alleged felonious assault, armed robbery and weapons charges, police said. He was hospitalized briefly then taken to the Schoolcraft County Jail.