This info is from Briley's webpage under the FAQ section....
Can I shoot non-toxic shot through replacement chokes?
All Briley Replacement Chokes up to and including "Improved Modified" will handle steel, tungsten, etc. Briley Replacement "TITANIUM" Chokes are for "LEAD ONLY". Briley "THIN WALL" chokes must state "FOR STEEL" on the side of the choke. If not then "LEAD" shot only may be used.
There is also a chart on the same page with lead to steal choke conversions.