I am shooting a pretty stiff load of Retumbo in my 700 STW. What are some of the things I can have a smith do when I send it in to make it a little more safe and more able to handle these higher pressures?

Thanks
Big-un

you can have it freebored. Not much else I can think of.

Very little.The only way to increase safety is to reduce the pressure.

To improve support around the case head, you could cut a custom chamber with minimum clearances, and have the barrel set up with minimum clearance between the bolt face and the breech of barrel. Bush the firing pin so that the primer can't flow back into the firing pin hole.

Normally all those things are pretty decent on factory Remingtons, so there's not much room for improvement unless you have an exceptionally bad example.