I contacted Smith&Wesson by email. Got the answer today. They say my 642-1 is Not rated for +P ammunition. So I guess that answers that.
I just remembered how I got one box of 38 spl. +P ammo. I don't remember what store I was in but I noticed they had only two boxes of 38 spl on the shelf. One was a one hundred count box of Winchester 130gr. FMJ Target. The other was a 50 count box Winchester 130gr.FMJ Target. I bought both and put them in my ammo cabinet. I think it may have been a couple years later I pulled out the 50 count box and opened it up to find that they were 38 +P spl hollow point. The one hundred count box was 130gr. FMJ Target. I still have both boxes. Anyone have that happen before?