I've started the conversion of the Iron Kingdoms setting to Runequest. I figure that the tech level of the Iron Kingdoms is approximately equivalent to the 18th Century, although with a few technological advances (such as rail travel).
However, my intention is to consider the damage ratings of the guns in the setting, and standardize them to the same dice used for damage modifiers for high strength. Basically, no gun will do 4D4 damage -- that model will do 2D8 instead. The motivation behind this is to 1) standardize damage, and 2) make gunshot a little more survivable by making low damage results more likely.