sally,

Thanks for posting those pics. Incredible.

Mine has the same casing marks on the recoil shield/breech but none of the odd scuffing and scrapping. And my spent cases have never looked like that.

I agree with your engineer friend, you need to have S&W fix that. As for two guns in a row from the same dealer having the issue, they must have been from the same production line batch. Amazingly bad luck, but hopefully good luck from now on.