I think you did a good job and have great skills. However, your finish appears a bit flat to me unless that is just the lighting and does not have that german bluing hue you find on a MP40. I have talked with John Andrewski (JA) regarding bluing on a German MP40 and he gets close to the look of an original MP40. I love how mine turned out after John did the refinished it.
If it was me, would talk with JA and have him do the refinish so you get close to the original look as possible.
However it is your MP40 and if you like it, then please ignore my above comment.