RR; From the view you show yours looks more like the original, note the step down at end of block. Mine, which is marked Modified Diana looks just like the one Pete shows, with the steel block & twist bbls with no step where thay join. I do not know how many methods of construction Pieper may have used, but his original patent shows the bbls without a step being inserted from rear of breech & fit to a slight taper in the block. On the modified version the tubes are stepped down & insert in the block from the front, as is customary in modern guns. On the one I have the tubes only extend back about half way through the block so the rear of the chamber is cut in the block itself, with the front part being in the tube. The tubes on this type are I believe threaded into the front of the block. Perhaps yours is a sort of hybrid between the two with the tubes being smaller than the block, but still inserting from the front. Can you determine if there is indeed a joint on the inside somewhere in the chamber. Mine was in poor condition with the forend lug & under rib loose & needed re-laying. I decided to apply a little heat & when I did a solder line popped out about the middle of the chamber, which had been invisable. From this I was able to determine the tubes did not extend full length through the block.
