Steel shot W_A_S hell on barrels.
The modern steel loads have much progressed in the last 15 years. Shotcups are much thicker,all but eliminating barel scorching, better powders have been develloped and steel is probably as good as it will ever get.
However for steel, 24/1000 constriction is tight.
I too have a lovely open choked Sauer SxS which I will never shoot with steel. Not because steel scorches the barrel it does not with thick plastic wads, but because our Sauer was not designed to take the much higher pressures of the steel loads. Your Sauer would sooner then later shoot loose.
European light doubles are not designed to shoot heavy pay-loads. They kick too much in those light guns.
I have a dutch friend who has a beautifull open choked Merkel SxS which he shoots with heavy Fiochi steel loads. First of all it kicks the hell out of you, the barrels are not scorched, but the gun will shoot loose a lot faster.