Girardo said
I have a model 37A that was in an in-laws attic a long time. I cleaned it with Hoppes #9 & 0000 steel wool. The trigger will cock with the barrel break open but if you snap it shut the trigger will only pull back about half way. This happens with or without a shell inserted. Any ideas. Thanks

  

Spray some gun cleaner in the area of the hammer and anywhere else you can get it into the action.