Kranix and Patrice,
My information on the giant guns comes from two sources, one a web site, an excellent and detailed work: (http://www.cix.co.uk/~nrobinson/railgun ... index.html
The other is a book by Ian V. Hogg "German Artillery of World War Two" Greenhill Books, London, 1977.
Kranix, I do have one correction to make and that is on the reloading times for the 80cm guns. The site quotes a figure of "At best as little as fifteen minutes was needed to load and fire a round. . .more often the interval was longer". According to the web site referenced above I also fond the following:
"The preparation for each shell and charge was considerable and involved several stages including taking the temperature of each charge, accurately computing the air temperature and wind currents at altitude, and getting the shell and the charge to the breech. Projectile and charge then had to be rammed accurately, and the whole barrel had to be elevated to the correct angle. It all took time."