Marlin has advised owners of their old hammer pump guns that they are unsafe to shoot. I don't recall exactly why, but it seems like there was something about firing out of battery.
It's been almost 20 years so the details are a little fuzzy, but there was a period SASS Cowboy shooting where Marlin hammered pumps were allowed. There was a specific model when if it wasn't assembled correctly and/or checked on a frequent basis one of the safety features could fail which IIRC could cause the gun to fire out of battery causing the bolt to come out the back of the gun, hitting the shooter. This caused SASS to ban all pump shotguns except the Winchester 1897 in either 12 or 16 gauge and any replicas in those two calibers. The Marlins weren't very common and I only remember two couples who used them versus the hundreds of people who used the Winchester 1897.
Marlin, which had no control over these old guns and what ammo might be used, correctly covered themselves legally by saying the guns should no longer be used. The Winchesters did not have this design issue and apparently the Winchester company that made the 1897 pump shoguns had changed hand so many times that they could not be held liable even if there was an accident with a 1897 pump.
