As some of you know I have a Ruger No-1S that has been rechambered to 450 3 1/4" Nitro, well after a few weeks of scratch'en the head 3 smiths have told me the same thing, the chamber has been cut under sized, need to have it opened up some, any ideas on who to go to on this? Non of the ones I talked too will do it in my area

You will have to find someone with a reamer and that is going to be the tough part....It would be nice to find out who did it in the first place and use the original reamer to try and clean it out.

Looks like to me your chamber was reamed,that was step one.But never chased that is step two.Chaseing the chamber will true.