I feel your pain, do you have a picture of the mount itself? I had this very same thing happen to me a few days ago, with what might have been a Barska mount. It was very roughly machined on the inside, and I had to go through hell filing it all out. In the end I got close...and tired. I realized I had another bolt carrier and gave it a try, and it worked fine.
If your trouble is the same as mine, it was more than just the top of it that wasn't milled out enough...mine looked fine on the outside, on the inside it looked like an unfinished prototype.
If you can post a pic of the inside.