I am beginning to seek information, comparing actions on falling block single shot actions of the world, especially comparing German Christian Heeren patent, Hagn system of 1974, British Gibbs Farquharsan, American Ballard, Sharps Borchardt, etc.  Is anyone familiar with these actions, especially in the falling block/lever set-up on these--especially on the Heeren patent?  I want to compare them, mechanically, to see ways in which they differ.  Can anyone suggest places I should look for such information--I am familiar with American books on single shot actions, but need data especially on German actions.