I don't think a 458 would carry enough momentum to punch through dino skulls at any real range.
Dinos had really tiny brains. I don't think head shots would be the answer.
I like the flame-thrower idea. They would probably be afraid of fire, as most critters are. I don't think there would be enough portable fuel capacity in a scenario like this.
Liberals never met a slippery slope they didn't grease.
-Me
I wish technology solved people issues. It seems to just reveal them.
-Also Me