Actually rather far along on the road to CNC. The cutters are being guided by the thick template bar running across the front of the machine. You can see a roller follower contacting the template in front of each cutter. The next step was the optical photocell tracer, then NC, then CNC.

The photo also raises an odd question: how precise does the *outside* of a gun barrel need to be, other than at the mounting points? Looking at late-war Japanese weapons, the answer is "not very," although they were also compromised by poor metallurgy that made them a danger to their users. In all likelihood, the Allied requirement was that it looked good enough to encourage sailors to maintain them, and that paint would go on well enough to protect from salt accumulation.

where is the operator's safety goggles and ear protection?

I have been a machinist/tool and die maker my whole life. This is how we used to do things. Now it is done with computer numerical controlled (CNC) tools. I am still in the business and own my own shop equipped with several CNC machines. People that call themselves machinists today wouldn't have a clue how to operate anything like this. This is a dying skill.

Of note... the coolant that is flowing onto the tools looks like milk. It is actually a soluble oil. Mixed with water in the right ratio served the purpose quite well back then. It had an unmistakable odor. Not at all offensive until bacteria started growing in it. Then it got quite rancid. Now the coolants are synthetic chemicals. The smell of soluble oil on a hot tool can bring back a lot of memories to me.