Browning does not guarantee their B25 for steel shot and has since produced O/U with specially designed chokes (e.g. : the Invector chokes). I went through this when my country banned lead shot around waterways. I contacted FN-Browning and asked if my two B25's would suffer fron steel shot. They told me they most surely would and I consequently acquired a Browning 525 in 12 ga 3" with Invector "steel" chokes.
B25's 12 ga Special Chasse (no steel)
B525 12 ga Mag with Invector chokes (OK for steel)