Making the extractor cut isn’t hard if you have a mill. I’ve seen guys set up the barrels vertically on bridge port type mills and have the barrel hanging below the cross slide. My mill is a hybrid horizontal vertical mill and I had to set it up on the table and use a woodruff key seat cutter. It was not difficult. I was very meticulous about transferring dimensions from the factory barrel. BTW these cuts are the very last operation before assembly. You need to have the barrel threaded chambered and head-spaced to the action. I didn’t want any problems with indexing the cuts, so I torqued the barrel on and scribed the cuts and made an index mark on the the barrel below the stock line. I then removed the barrel and made the cuts so I would be positive I got everything lined up exactly right when I assembled it. You will probably find that the breach block is not squared to the action face. This was the case with my action. It was out like two and a half thousandths. I couldn’t conceive of any way to remedy this without machining a new breach block and I wasn’t about to do that. Turns out it didn’t matter as far as accuracy is concerned. Hope this is helpful
