What is this insert you speak of? Where does it go? Yes, it's in the slide, but where in the slide?
It's difficult, sir, to find a good image on Mr. Gore's internet because all of the non-video reviews that I have seen have used stock photos. So - this is the best I can do to show the insert. Insert may not be the correct term - but I have an M&P .22 Compact, with a similar feature, and I think S&W refers to it as an insert in that case.
I'm not in any way trying to discredit the pistol - I'm just curious as to why they used the insert. Poster bigwheelzip, I think, has answered the question; it's just cheaper and easier to machine the insert (and then pin it into the slide) versus the required machining operations on the slide itself. I would expound a little on his comment by saying that they would ruin a slide if a CNC error was made making small cuts on the slide itself; whereas they would only have to recycle an insert if the same error was made on just an insert.
And, again, I'm just waiting for them to show up, I'm going to buy one!
Edited to add: Did some more thunkin' on this and, finally, realized that pinning a steel insert into a steel slide isn't new at all. SIG was doing it at least 30 years ago ... with the stamped/folded slide pistols, with pinned steel inserts, such as the P225, P220, etc. The
ONLY reason I brought up the subject of aluminum is two early reviewers both commented that the slide appeared to me made of lightweight material.
Added #2: The winky-face in my post, a few posts back, (about the tactical paint eating into the aluminum slide) means that I was joking about the slide being aluminum. As I have mentioned in another thread on the .380 EZ - I stand corrected, I was wrong about the slide being made out of aluminum.