Rob Kardashian Selling Tickets ... to the Gun Show!

0128-rob-kardashian-working-out-INSTAGRAM-01Looks like it's chest day for Rob Kardashian.

His chick, Blac Chyna, documented his bench press reps -- although she conveniently kept the bar and the weights out of frame.

We don't know how much Rob's lifting, but we can say his arms are looking fit.