Here is picture of a falling block a guy on Weaponsforum
has picked up to finish. The fellow who started building
it laid it aside for awhile and the new guy is going to finish
in BMG. It has 50cal bbl on it. Looks easily big enough
for 12ga,10ga,8ga, my 700s. The lever on left is cocking
mechanism, The tube in back is a firing striker and spring
and it hits the hammer block you see in the back of the
breach block, which hits firing pin ahead of it in breach.
It is the the only one like it. They've put a lot of work
into it, especially the hammer block striker setup.Ed