Usain Bolt Blastin' Bubbly with Champagne Gun in Cape Town

Usain Bolt was locked and loaded in Cape Town this past weekend ... tearin' up the South African party city with the help of a gold-plated champagne super soaker!!

Bolt rolled through local hot spot Grand Cafe & Beach with a small entourage -- poppin' bottles, smokin' cigars and (of course) gettin' his groove on.

The retired sprinter's Sunday Funday wrapped a little before midnight -- but not before he blasted his homies with some heavenly Brut.