Angular / Asp.Net Web Api request binary data

I have an Angular 4 application which consumes an Asp.Net Web Api, and I want the Api to return a binary file. The Api route seems to be working correctly - I tested it using a rest console and the response is as expected. However, when trying to use the same route in the Angular app, the request sends but returns an error. I can see with the C# debugger that the request is executing completely and doesn't fail on the server. Here's the error in the JS console:

This error occurs on all browsers tested (Chrome, Firefox, IE, Edge, Safari).

Here's the server side code:

[Route("api/getfile")]
public IHttpActionResult GetFile()
{
    byte[] file = <file generator code>;
    System.Net.Http.HttpResponseMessage responseMessage = new System.Net.Http.HttpResponseMessage
    {
        Content = new System.Net.Http.StreamContent(new System.IO.MemoryStream(file))
    };
    responseMessage.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/octet-stream");
    responseMessage.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
    responseMessage.Content.Headers.ContentDisposition.FileName = "file.pdf";
    return this.ResponseMessage(responseMessage);
}

And here's the Angular code:

let headers = new Headers({
  "Accept": "application/octet-stream",
  "X-Requested-With": "XMLHttpRequest",
  "Authorization": `Bearer ${token}`
});
let opts = new RequestOptions({headers = headers});
opts.responseType = ResponseContentType.Blob;
// Uses old @angular/http, not HttpClient
this.http
  .get(`${apiUrl}/getfile`, opts)
  .map(res => res.blob())
  .catch(err => handleError(err));

EDIT: I tried using a plain XMLHttpRequest instead of Angular's Http service and it works. What do I need to do to get this to work with Angular?

EDIT 2: It works if I fetch an actual file on the file system that's accessible using the same host that the Angular app is running on. The Angular app is on localhost:8080, while the api is on a different port. If I expose a file on localhost:8080 (e.g., in the build folder) than I can fetch that file. This makes me wonder if it's a security issue, or maybe has to do with the headers or the way Web Api returns the binary data.

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