CHEYENNE, Wyo. — In the "Cowboy State," where guns are present in more than half of all homes, an unlikely battleground is forming in the fight over the appropriate use of firearms. Flush with victory in its push for state laws allowing concealed handguns, the National Rifle Association is lobbying lawmakers here and in 11 other states, including Arizona, to make it easier for people to defend themselves with deadly force. The NRA, backed by a growing membership of about 4 million, wants legislation specifying that people have no duty to retreat from an attacker before using deadly force. About...