Chuck --
Your posting outlining your restoration work on the Parker is remarkably interesting.
The fixturing you show in the photos is substantiallty self explanatory in most respects. But, how did you control the spacing betwen the barrels? You indicated and the picture shows the barrels are in contact at the muzzle. I assume that the chopper lump provided another point at which the side to side position of the barrels were fixed. Did you use spacers along the seam betweens the barrels to eliminate bowing and to provide for barrel straightness and parallelism between the barrel bore axes?
Additionally I assume you may have used "soft", Tin-Lead, solder ( and not a brazing alloy) to join the barrels. The required fluxes for soldering to steel are often corrosive. Was there a potential problem with flux entrapment within the solder joints? How did you "handle" this potential problem?
Thanks,
Regards,
Don
