Senor Jabali, there are a couple of articles about the Martini-Hagn action on the web which you can google up, one written by the gunsmith who is doing mine. He thinks (and so does another head of a large London best maker) that it is probably the strongest and most functional single shot action ever made. I am having mine made by Hughes for a number of reasons but at the moment with the dollar where it is they are great value I think. Mine will be a 1 piece as the extra $5000 or so didn't seem worth it to me. That same "head of a best London gunmaker" with whom I was sharing a pint with recently mentioned they maybe considering buying a few actions and building the rifle up themselves and the price was considerably higher:),
best, Mike
p.s. if you are going to use it in Spain or for travelling in Europe, the .30-06 might be a better choice. If you pitch up at your local gunshop here asking for some improved .303 rounds you might have a long wait