I'm not claiming Riddick to be better with a gun since he didn't use them nearly as much as h2h or blades. I'm just pointing out that he can use a gun well enough that Dredd won't be standing there while shots miss left and right.
EC
Esau CairnContagious
Riddick's constantly proven to have deadly accuracy when it comes to knife throwing & timing his moves for the perfect kill.
I can easily see Riddick disarming Dredd & taking him down.