Justin Bieber Was Just a Regular Guy Slamming Shots in Boston Bars

If Justin Bieber's got beef with his fans, he didn't show it as he partied hard in a couple of Boston bars like any other 22-year-old ... who can afford round after round of shots.

After his Purpose concert Wednesday, Justin hit up Storyville nightclub and looked totally comfortable being the life of the party. He was up on the bar doing tequila shots, and didn't mind people taking photos. A rep from 6one7 Productions tells us he racked up about $2,400 worth of tequila and vodka.

Cool moment in the video -- the DJ bumping Justin ... Timberlake, that is.

Biebs started his night at The Tam ... a joint most locals call "a dive bar." We're told he drank Sam Adams, ordered shots of Fireball for a table of guys and girls and was "super nice" to everyone.

Even though his bodyguards made everyone put down their smartphones -- no "zoo animal" pics -- watch this video ... you can tell folks in The Tam treated JB like any other booze hound.