So I recently purchased this 870 and had a few things that I didn't like about it. The trigger being one of them. I couldn't help but notice that the trigger is already narrow but it was flat with sharp edges. I went to the range tonight and went through about 50 rounds and made my finger raw just as I figured it would.
So it was time to break out the file! I tried to get a good shot of the edges but you can't really see it that well. I also left the trigger in the housing for stability. Here are some photos of the progress.

A little tape to prevent scratches on the trigger guard



And the finished shape