I assume the gunsmith with 40 years experience who actually examined the gun knows more than the $10 an hour customer service rep at some phone bank
BUT.....
and the gunsmith could not determine what was wrong with the gun
Someone else also said this sort of contradicts its self.
I can only imagine how many times S&W was told this guy is a "qualified smith"!
So now with emotions high, you run call S&W & tell them the same thing.
Like another guy said;
not having been in on the first call you made to them
....it is hard to guess what the conversation was like!
If you called up
(not saying you did, just an example) yelling about after the third round the slide locked back & can't be released. And how an extreamly qualified guy/gunsmith, who works at the range that could have sold you the ammo, says it definately is not the ammo & it is without a doubt a gun malfuction!!
I can see how things could take a turn down a side street!
Again, not being there for the call we can only turn to what we know about the parties involved! That is simply the companies reputation!
Thousands of post stating how great the company is! This builds the reputation!
If it were like other companies with every other post complaining about thier lack of service, I'm sure everyone would jump in line!
NOW, with that being said I agree that the result, how ever it was arrived at, was not the result that you or the an upstanding company would want!
I think the CS rep was on the defensive. The only thing that they could do is a quick diagnosis which is the same thing that most of the members did here. They assumed that the barrel was buldged & that is was an ammo/operator problem.
I am not a customer service boss & I don't play one on TV!

But here is what I would do:
1) Focus on your goal!
Does it really matter who's fault it is if you get your gun fixed?
2) Call S&W CS back!
I will again quote other post:
keep the implication of litigation out of the conversation
Something my father once told me about "honey vs vinegar" applies here
describe the problem without attributing a cause to it
Ask them what would be the best course of action to reach you goal! Ask if they can take a look at it a to see if they can make it work again.
The main thing is to get your gun back to a working condition so you are either comfortable with it as a SD gun or so you can sell/trade it off.
I feel bad that you are having trouble with you gun.
I really do hope it all gets worked out to your satisfaction!
Try to keep your wits about you & a cool head!
I promise loosing you cool will not help. Believe me, I tried that path for years!!
Best of luck with the rest of this journey!
Keep us updated!!