What's optimal in weight is very much a personal thing, and also connected to the purposes for which the gun is intended. I shoot the Lancaster about as well at sporting clays, using 7/8 and light 1 oz loads, as I've ever shot anything. Doubt that would be true with a Brit 2" 12ga, weighing closer to 5# than 6#, but it might make a dandy ruffed grouse/woodcock gun.
Part of the reason for weight in today's guns is to accommodate today's loads. Specifically, in the case of the Spanish and Spanish guns intended for the American market, American loads. Those require a heavier proof than similar guns shot with traditional European loads, where 1 1/8 oz is on the heavy end for a 12ga game gun. Most of the time lighter. Recent British guns, IF subjected to the Superior proof (old magnum proof), are also likely to be heavier.
