Hi Gillaume,
I suspect that the bāton ā feu you refer is well under the weight range you are dedicated to.
Here you find some more info on this area, including the name of the Castle/Museum where the bāton ā feu is exhibited, from where could possibly enquire about the details you wish to know:
http://www.vikingsword.com/vb/showthread.php?t=10350
... I wonder if Cornelistromp reminds the material of the tube and the dimensions of the whole setup. In my imagination the tube material was iron, as i was under the influence of mounting my two examples following its style:
http://www.vikingsword.com/vb/showth...ght=castelnaud