I wouldn't really be that worried about keeping an unloaded weapon secured in the middle of a gun battle as bullets are flying in my direction. Among the few reasons for abandoning a long gun would be running out of ammo or not having adequate cover to reload it. If you're in a traffic stop shootout or using a pump shotgun, then having that kind of set-up could be a good idea. Otherwise I'd much rather take a few seconds to reload a rifle if there's cover to do so.