This is a genuine question but why do you feel the need to drive around with that in the trunk? Is it for protection?
I only ask as we obviously can't buy anything like that on this side of the pond.
In many states you can carry a hand gun but must have training and get a permit. Rifles like this and other types can be carried without a permit but should not be loaded in a vehicle. The ammo should be stored separately for safety.
Most do not carry rifles full time. They might carry them to go shooting range or this type of gun can be used for deer hunting. Does not look like a hunting rifle but they are accurate. 7.62mm gun works best for deer hunting.
With terrorist and other attacks occurring more in the USA I hope people around me are carrying or have access to guns like these. If I do not have one at the time, then I will help carry/load ammo and spot bad guys.
Many think the USA is gun happy if you listen to some, but most owners are model citizens. There are a few idiots who make a bad reputation for the rest.
We are not nuts, and one day a gun owner might save the lives of people around them.
Practice gun safety for all.