No question, any of these gunmakers have a bunch of tricks that probably took decades to work out. I enjoy watching some of the Maker videos on Utube and see the hand finish work that goes into a gun. Basically, the machines get rid of a lot of unwanted metal fast. My idea on the lumps: if you note the forearm fit to the barrel, it appears to make up about a 9+mm 'hole'. My idea is to drill such a hole first in the lump before turning it into bites. I have to figure some way to mount the lumps in the block in some temporary fashion so as to be able to silver braze the pieces together. The object to get as good a fit as possible to lesson the hand work.