Angular $http.jsonp or get returning 404 on a mobile

I am pulling in JSON from a file I am storing locally. When I view this in the browser it works, when I view it in an Ionic packaged app it returns 404

I am using the following code:

.factory('cardFactory', function ($q, $http, $rootScope) {
  return {
    getCards: function () {

  var deferred = $q.defer(),
    httpPromise = $http.jsonp('/static/cards.json');

  httpPromise.then(function (response) {
    deferred.resolve(response);
  }, function (error) {
    console.error(error);
  });

  return deferred.promise;
}
};

});

And calling it like so:

  cardFactory.getCards()
  .then(cardSuccess, cardError);

I have tried with GET instead of JSONP, both return a 404 response.

I am aware of the access-control-allow-origin issue, but surely the jsonP should solve that? This is at the same level (hierarchically) as my images, which are served fine.

Any ideas what's going on?