I don't know how valuable this information is, but while visiting the Remington website I read their reply to a question on whether steel shot could be used in their Spartan doubles. They answered that it could if the gun was choked IC/C. I believe the tubes in those gun are NOT steel approved but apparently the IC/C chokes(according to Remington) suffer little from steel shot. I should mention too that the rest of the bore is chromed. Except for your modified choke (with smaller shot) you maybe ok? One of the other members here, uses steel in his older American doubles and has had no damage to his gun bores, but did note that the heavy waterfowl loads tend to crack stocks.
Best to you,
Kurt
