I suspect there are Citori 12 frames out there that have been fitted with 20 gauge barrels, much like the Beretta 68x guns. But, my two field Citoris in 12 and 20 have different frames. The 12 is a standard 1970's 12/28/3" hunting gun, while the 20 is a mid-90's Lightning. I also had a Lightning in .410 that weighed a bit more than the 20, but I don't remember if the frame was any smaller.