^^^Yessir!^^^^
The equipment matters but being done in a single setup can not be reproduced on any machine. Further, most new machines...even top of the line cnc stuff, won't hold better than a tenth or so...brand new....much less the wwII era lathe in someones basement garage.
A test fixture has standards. At worst, it should be capable of half of the claimed tolerances and 3-4x is better...and this assumes superhuman perfection from the operator that sets the part up for testing/fixturing. Tenths get tossed around like child's play in this industry. If it was child's play, you'd think companies like Haas would build a machine that is absolutely perfection, regardless of the environment it or the tools to measure it were in.
The saving grace is that most barrel and receiver work is done a short distance from the chuck and a reamer induces far less bearing and tool deflection than a typical cutting tool. There are so many variables when talking about holding .0002" or better tolerances in a production environment that it's not funny. I gave up a long time ago at trying to convince people of these things. I'll just say this, and it might make some people mad....If you're smith can guarantee .0002", you should either marry him or run away as fast as you can. You get to pick which. I did true tool and die work for a living, on top flight equipment and in a controlled environment. Mics were checked every morning and sometimes several times a day. Tip...you can't hold it in your hand checking it several times, until you get it to read what you want it to.
Truth be told, top flight gun work is rather crude by comparison. Lets say that I can true an action to absolute perfection...then sandwich a recoil lug that is .0005 or considerably worse, between the action and the perfect barrel. What was gained and how many here have measured a perfect recoil lug?
I've got the inspection report here for a brand new lathe. Brand new, straight from the factory the headstock bearings held .0002. Someone please tell me how I can claim better than the bearings that the lathe spindle runs on. Now, even if you can, please tell me how I can machine a part BETTER than the machine itself even after the part having been removed from its original setup and machined from a new setup in said machine.
Don't get me wrong...I've seen some messed up custom actions but with those, the problems were apparent.
All that said, if you want something truly to size, you polish or grind it to dimension.