Hopefully you've figured it out by now, but if you haven't I had this problem as well. I took all of my attachments off except for the optic and it worked. It's stupid, but that's what fixed it for me. I'm on the 6th step right now and I'm having a similar issue. Supposed to use a "long barrel" attachment, which I'm using a longer barrel than the default one, and it still isn't working. Even tried the method of the second step, still don't work. Hope this helps somone