The Game -- Accuses Ex Cohort of Chris Brown in Car Attack

The Game is going HAM on a guy who used to be tight with Chris Brown -- accusing him of masterminding the attack on Game's car and Chris' house ... but the guy's firing back.

Game pumped up the beef by calling out Wackstar -- a former CB posse member -- and saying, "Tell these fans who really had Chris brown auntie tied up & his house broke in you pu**y ass fa***t."

Homophobic slurs aside, Game also made a clear threat -- "When I see you I'm gone break yo f**kin jaw...So have yo gun on you pu**sy."

Wackstar seems unfazed by the accusations on Instagram. He called Game a fake gangsta, saying ... "I know the real you, you wouldn't hurt a f**kin fly." For good measure, he added ... "#ChangeOfHeartAssN**a" ... a shot at Game's past appearance on the TV game show.

For the record ... no arrests have been made in the Chris Brown burglary or for damaging Game's Porsche. Also, Wackstar is NOT the man seen in surveillance video Game posted.