I'm tempted to buy my first SxS soon. I'm considering one of the Spanish makers, like AyA or Arrieta.

What are the nominal bore diameters that the Spanish gun makers are using, for their current production 12 bore and 20 bore guns? Are they .729 and .615 respectively, or are they underbored or overbored?

I'm mostly interested in the 20 bores and will use the gun for hunting (pheasant, quail, grouse) but I would consider a 12 bore as well as a strictly pheasant gun.