Stan,
A Spanish gun that fires both barrels when one trigger is pulled is likely defective, it was not designed that way. Some Spanish guns are very good, but others have a reputation of having soft parts. Sears and sear notches are particularly known for that.
Mike
Mike I know of guns made and advertised to shoot both barrels when the back is pulled 1st or to work normal if pulled front then back. Pretty easy to build that way.
At one time the production side of Verney-Carron was selling Spanish guns like this to the European market.
