I have read about, tested and used commercial, well known brands of .22, .38 and .44 shotshells for many years in non-ported, "modern" S&W revolvers. Shotshells have come in very handy for head shots on both wounded turkey and upland birds hiding in bramble, and of course for dangerous snakes and rabid critters. Never had or heard of any substantive problem.
This year I purchased a Pro Series 637 with a PowerPort 2.125" bbl., but soon thereafter a Forum member posted a question merely asking about the advisability of shotshells in a PowerPort bbl. Nobody gave him an authoritative answer.
So, before using my new 637 with shotshells, I e-mailed S&W asking if (1) it would harm the gun or (2) it would be somehow unsafe even though many shotguns are ported.
The e-mailed reply was simply, "No, don't use anything other than the specified ammunition in your handgun."
That did not answer my question about the well-proven safety of ported shotguns, or about any harm to/from a ported revolver; the reply sounded like lawyer speak. I therefore telephoned the S&W employee who had e-mailed me and asked why he had simply said "no".
He replied that S&W revolvers "were not chambered" for shotshells ! "Even non-ported guns?", I asked. "Yes, use only specified ammunition", he replied.
"Why, then, do the well-known shotshell companies and gun writers say shotshells are absolutely OK in good condition revolvers?", I asked. "They will say anything", he replied.
Now, gentlemen, I want to play it safe, so I ask you: Is there any reason you know of why I should not use shotshells in my new Model 637 PowerPort revolver? (Of course I will disregard his advise regarding non-ported revolvers.)