Ronda Rousey & Mark Wahlberg Break Out the Guns in Vegas

It was an arms race in Vegas ... with Ronda Rousey and Mark Wahlberg flexin' all over the 2018 CinemaCon ... and left everyone in the crowd feeling weak as hell!

The two were pushing their new movie, "Mile 22," during the event at The Colosseum at Caesars Palace ... the flick in which Mark plays a jacked CIA operative.

Remember, Ronda was shooting scenes for the movie in Colombia a while back -- when she snuck back to the U.S. for the Royal Rumble ... where she announced her WWE contract.

"So fun getting the gang back together again," Ronda posted after the event.

Now, it's back to wrestling ... where Ronda will most likely clash with, and then murder, Mickie James.