too be safe, I would have a gun smith check out your gun, particularly the barrel wall thickness but if it were me, I would have little concern shooting the RST lite loads.
There was a test conducted by Sherman Bell in a resent Double Gun Journal in which he tested a damascus side by side versus a set of old steel barrel with increasing loads until catastrophic failure. Both went about the same and it was WAY WAY more pressure than even modern SAMMI specs. I don't recall exact numbers but it was somewhere better than 20,000 pounds and I think the RST are rated around 7000.
