Tomac
A couple of questions
1. Was the mag fully loaded?
2. Did you use the slide stop?
Many have found with fully loaded mags the pistol will fail to go completely into battery when the slide stop is used. Most of those issues are eliminated by using the "sling-shot" technique. If you are not familiar with the term, next time load the mag fully and insert then pull back on the slide and release letting the it slam home with full force. Now if you didn't answer yes to either of the questions above then disregard my rambling