We work on alot of doubles and here is what we find. The current production guns be it Blaser, Heym, Krieghoff, Francotte, Chapuis all are great shooters. Not so much for the english guns unless great attention is paid to custom loading for the specific gun. Currently I have 2 real Rigby's that we are doing some minor work on. The first is a .303 re regulated sometime in the 70's. It is a wonderful shooter about 3" at 100 yds with both barrels. Out of the box the blaser 30 06 was a ragged hole for both barrel at 100 yds. The other gun is a .470 Sidelock Rigby, I must say this is the true essence of a double, but you are a minute of a turkey platter at 50 yds with Federal and Kynoch. As a control I took my Chapuis out and put 2 shots about an 1" apart on the same target. The Blaser shot a duplicate group to the Chapuis.
The best shooting British double I have ever shot was a .375 Flanged Royal Ejector built in the 60's. It was scoped as a driven boar rifle and would shoot ragged hole group at 100 yds. With sights at 50 R&L was no more than 1/2" apart. I prefer my Blasers and Kreighoffs still.

Aleko