as to field grade 12 gauge double guns being disassembled for parts...

given that the market for assembled guns is declining, i dont see a market developing for their parts.

besides, putting together a double gun from parts from other guns is a hit and miss thing; requiring considerable gunsmith skills and lots of luck.

if there is no demand for a gun, then why go thru the effort and expense of creating one?

keep it simple and keep it safe...