If they ARE bored straight through, then you have a factory defect & I'd be calling S&W on it.
If they still have any cylinders for that gun laying around, they should send you a pickup & replace the cylinder for nothing.
But- inspect the chambers carefully, from both ends.
Use good lighting & somebody with good eyeballs.
If necessary, run a narrow object like a dental pick, nutpick, or even a nail down the internal walls from the rear & see if it runs into a shelf before it exits the front end.
And, Mike's a good man, when he's not cartin...er, horsing around.
Denis
As I think about it, another easy way to tell is to try to insert a LOADED cartridge into the front end of the chamber, with the cylinder open.
If it'll allow anything but the bullet inside, you have a straight-wall chamber.