The bar metrics properties you can set on a UINavigation bar are things like background image and the title vertical position. Heigh and width need to be set from within your view controller.
If you need to manually tell the navigation bar to change it's size when the orientation changes you can implement the method - (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration1
in your view controller and change the size there.
Another option you can use is to use autolayout to specify that the width of your navigation bar is pinned to the left and right sides of its superview and let it figure out how wide it should be. For example
UINavigationBar *bar = [[UINavigationBar alloc] init];
bar.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:bar];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[bar]|"
options:0
metrics:nil
views:NSDictionaryOfVariableBindings(bar)]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[bar(44)]|"
options:0
metrics:nil
views:NSDictionaryOfVariableBindings(bar)]];