One of the top names that does not tout CNC work is Boss. Cannot tell if that means they do not use it.

For a detailed look on best gun building in the UK via CNC look at the Boxall and Edminston site.

As for hand filing. There is a huge difference between filing a rough forging and finish filing a CNC part. To expect rough filing today considering the technological advances mentioned by Gunmaker above borders on sadism against the worker.