CORRECTION!
Sorry!
The main part of the stock is 49mm. And so is the part I dimensioned as 49mm on your drawing, AT THE TOP, where it chamfers down to the smaller butt end.
HOWEVER, the thickness of the butt at the point with the two recessed circular "fastener" details is less than this - it's inset slightly. Same part, but different thickness. 46mm.
Does this make sense?
Sorry for the bum steer, but hope this helps.