Tacticool,
I was getting ready to update my previous post when I saw you had replied. Thanks for your clarification of what needs to be done.
I did not understand that you meant the whole length of the channel needed to be deepened. Thought you were just referring to the raised area of the channel at the front, and the nub on top. It took my son about 5 minutes of filing to remove the raised areas on top of the channel hole and nub on top. Then it was apparent that the whole channel needed clearancing.
Have reread your post several times before and after modifying our handle, and still would not have figured that out without doing our own handle. Your post made it sound like just the hole at the end needed relieving, and the nub on top removed, nothing else. Which is what several others have done with success.
A friend of mine has a mill and will see if he can cut the channel out for me next week.
What is confusing is how the fit of Raptor handles is so different for several S&W M&P10's. M&P10 Owners on this and other forums only need to just remove the nub on top at the front, or just remove the step in the hole at the front. Most need to do both. Mine is like yours that needs relieving the whole length of the channel. Even a very few have had them drop in and work right out of the package, which doesn't seem possible. Has there been a change in design or production of Raptor Ambidextrous Charging Handle, with both old and new designs still in the distribution system?