open up the ejection port

[ARlife4me]

I have a MEGA arms upper (armalite cut) and would like to get the port opened about .100" larger for short mag cases. Possible some more upper also to be done, but for now just this 1. How has a machine to do this and hopefully close to me as possible?

 

[ARlife4me]

For the uppers that I do have only the lower portion has been cut as to keep the port door being able to close. I'm wondering if the top would need to be opened also due to ejected direction?