Hi Alexender,
Nice to hear from you again!
Please see my photos in my thread:
http://www.vikingsword.com/vb/showth...h+loading+1540
Especially see post #5ff!
That system of locking the rear section of the barrel of a breech -loading piece by bolts activated by pulling back the rear sight, obviously was invented in Augsburg in the 1530's; it is first known from this wheellock arquebus dated 1540, and from other contemporary pieces, and it basically remained unaltered for centuries thereafter.
Best,
Michael