Stan, I would disagree with your exchangeability of other double gun barrels. I have been shooting a 687EELL Beretta for many years, at one time I had 4 different barrels that all were timed OK. Also exchanged barrels on a different 682 and my son's 680.

The Valmet's did not really take off with the target shooters, went to the same place as Rottweill's and so on....good guns, poor marketing etc....