Pete; Very interesting post. The first pic is constructed according to Pieper's patent. The one piece block is bored on a taper with the holes larger at the rear & the tube inserted from the breech end. the tubes themselves are not stepped which is why the block is larger than the bbls. I have a Pieper similar to the lower pic marked Modified Diana also but had doll's head rather than cross bolt. On these guns as best as i have been able to determine the bbl is stepped down, the shank threaded & then screwed into the front of the block. The tubes extend only about half way through the block so the chambers are partially in the block & partially in the tubes. I am still somewhat confused on the Pieper "Demi-Block". Normally we think of this as a chopper lump construction. The pic of the model 459 thouigh is marked Demi-Block but also shows the tube joining line. Is this a "Tubed Two Piece Block" rather than using the one piece mono-block???
