This is just common sense, I got in trouble plenty of times for having airsoft guns out in plain view while walking around my old sub divison. Now the only chance my neighbors have to see my replicas is if Im too lazy to put it in a case before it goes in my truck. However I am 22, and can legally own firearms so Ill do the same thing with my AR15 if I feel so inclined. Its best to hide your gun as much as possible though, even a black trash bag is better than nothing.
Its not really the cops you have to worry about, its your ignorant neighbors that wouldnt know a .22 from a ak47, heck most LEOs dont know much about the firearms that they dont work with. So it wouldnt seem odd to them that a guy in jeans is carrying around a G36k, they just see it as a firearm. I read an article not too long ago that stated somewhere around 65% of all new recruits going into army basic training have never fired a firearm, and if those stats only describe military recruits then imagine the general population.