AR15 lock up
#2
Leave it at home. It's to large to lock up in a place that is easy to get to when you need it. If you can't get it out in less than 30 seconds, it's would be a waste to have it in the truck and take the chance of it being stolen. And this may be a shock to some, but criminals surf these sights getting ideas of how to steal trucks, and what people are carrying in them.
#3
I agree if your carrying something for protection your better off with a pistol. And to second that even if you have a permit im pretty sure to have a rifle locked and loaded regardless is illegal and the ammo should be split up. But its to big to really do anything. unless you could fabricate something for under the back seat. If I need rifles locked up i lock them in the tool box in the back. Its not fool proof, but it would take somebody with smarts and a few minuets to try and rip that tool box out.