Indeed the three barreled gun is the most interesting thing. As you know, we have a long tradition in building Drillings as we call them in Germany. A well known gunmaker, surely one of the best, once told me that there was always one real challenge: to build a best Drilling! Especially because of the weight and the balance. Such Drillings have been build in former times. With two shot- and a rifled barrel they had 2.8 Kg! Length of barrels of course 68 cm or even more!
The new Manton Drilling is a so called "Sortenreiner" or "Flintendrilling" because of the three shot barrels. But the challenge is the same and it seems as New Manton has done a nice job. It's something very special, but I love special things.
BTW there is a nice Flintendrilling shown in the Westley Richards Bicentenial Book!

Kind Regards,
Gunwolf