That's really the one fault I see so far with this vehicle. Those civy tires will not stand up to much.
It's hard to say if they have runflats in them. But they're certainly beadlocked.
I think they should have ran 12.5R20's with beadlock/runflats in them. But I suspect the civy tires is what allows the speeds. 365/85R20's would be another option as well. I'd question most pistol calibers being able to actually puncture a more substantial tire. (Save a few very high velocity rounds)