Pugwash,

Re your comments about barrels "rotating backwards" and the various means to resist the effects of this phenomenon a gent on this forum built his own Winchester 21 double rifle (.45/70) and, If I recall correctly, he left more material behind the breechface in order to provide strength there.

Another consideration in building these rifles !!!!

I wonder, at times, how some of these historic doubles, with relatively few lockup features manage to "close like a bank vault" after a lifetime of use.Though few of these guns would see use of the kind that a Clay target shotgun would..........perhaps these guns would provide the stepping off point for alot of double rifle design......particularly the sxs live pidgeon guns.

Some of these double rifles seem to be just A&D types with no crossbolt, side clips, third bite etc.

Surely it is the result of correct fitting of barrels (on face, spring and effective engagement of rear lump/draw) along with effective hardness and design........what else would it be?

If this is the case then alot of additional lockup features must, effectively, be unnecessary !!??

I particularly liked your comment re lengthening bar/water table in order to reduce gape.

I have a theory that the water table/bar should be as long as the cartridge but have no basis in fact/knowledge to support such.

Pleased you took the time to set your files aside and share your knowledge with us.