This might help Jeff
https://www.shotgunworld.com/threads...-shoot.366087/
Checking the barrels for safety means having the barrels evaluated by a barrel specialist with the interest, equipment (wall thickness gauge and bore scope), and expertise to properly do so. If the smith can't tell you wall thicknesses from breech to muzzle, or states "should be safe with low brass", you need another opinion.
In light of the age of the wood (not the barrels) it would be reasonable to stick with 1 oz. at 1200 fps target loads. And of course NO STEEL.
I clean my pattern welded barrels with a
brass Tornado brush.
https://www.proshotproducts.com/12-G...USH_p_715.html
In the unlikely event that the standard stainless steel brush would fracture, the sharp edge
will gouge a damascus barrel.