Rob on AR is building a 12GA FH double on a Zabala Double 10 gauge frame. It has the Greener crossbolt. He cut off barrels to make a 4" long monoblock double to screw a pair of heavy 12ga rifled Pacnor barrels into. He reamed out monoblock section and threaded it. His barrels are 1.116" at the breach, .97" at muzzle and 22" total length. Barrels threaded into monoblock with a 15/16" x 32 thread. In the pics it is partly done and he will put in the ribs and integral sight rib and regulate for accuracy. It will be about 14.5 lbs when done he says.Ed