At least a couple members here have put together similar pumpers. Van is one that comes to mind. I found some of his threads, but it looks like the photos were hosted by photobucket and are no longer visible.
I have some spare parts I could use for a build of that kind: M4-177 pump tube assy., steel breech, LW .177 barrel, even the wood to make a nice stock. Wonder if a QB78 trigger group would work with the Crosman tube. Thanks for the idea David (you enabler )
Check out airgunsnirvana on YouTube.
rsterne made one i think... 2260 trigger and modified stock.