k3030AI
I have some trouble to understand your observations about the truing of the action on "modern" made custom Mauser rifle.
The rifle photographed on the first photo isn't a DORLEAC rifle (the second one is) but a genuine Rigby No.1 intermediate action made in 1906 for Admiral Sir Roger John Brownlow KEYES. The action bears the "WAFFENFABRIK MAUSER–OBERNDORF A/N" marking rolled on the left sidewall and the barrel the "John Rigby & Co – 72 St James’s St. London" address.
You will notice how faultless is the barrel fitting and the wood inletting, even with a not very good light.
I have owned that rifle a long time and I owe to the true to recognize that it was flawlessly assembled with a well squared receiver and a perfectly fitted barrel.
I don't think that the rifles made by Mauser or finished by Rigby before WW1 were hastily finished with rounded corner and "unsquared" actions…all the bolt action of that period I was lucky enough to have in hands (...and I have seen and shot a lot) were certainly practical, but also superbly build.
Honestly there is not any disadvantage to use a trued and squared action on a plain modern made open sights rifle.
Hope you will understand my not very good English.
All the best.

DORLEAC
www.dorleac-dorleac.com