Hello Rolf,
I remember the Falling Block Works action!

The only things I can speak to would be to:
Suggest a finished weight of at least 11 1/2 lbs (5.21 kg). Yes, it could possibly be lighter, but why? Range shooting & not carrying for hours on a hunt so no need for an ultra light rifle.

A nice fairly dense straight grain walnut (quarter sawn with a little figure in the butt area) for a stock.

.500 NE, .505 Gibbs, .500 Jeffery, .500 AHR……..all are attention getting on either end.

I cannot remember, does the FBW action attach to the buttstock with a thru bolt or does it use bolts thru the tangs similar to double rifles or the Winchester 1885 High Wall?

- Mike