One of my gunsmithing mentors used to bring me challenging jobs once in a while.
One was a stamping,a linkage to a safety on a Franchi double.I had two pieces.
I used an Optical Comparator and other inspection tools to make a drawing,then machined this thin walled part out of a block of pre-hardened mold steel(P-20).
He needed a tang for a Lo-wall Win,a Winder Musket. Made that out of P-20,also. Radius and angle dresser and the surface grinder helped on that.
In my experience,just finding a way to mathematically define the part is the first challenge. A big optical comparator helps a lot!!
Also,remember what tools they used long ago. I cut the breech mortises through a Hepburn receiver casting with a keyway broach guided by a fixture I built.
I looked at a Rolling Block extractor and thought "Shaper". I don't have access to a shaper.
I bored a deep hole in a bar of 1 1/2 in or so 8620 steel to match the ID bore of an original extractor. The bar was about 8 in long. I used a brass plug in that bore to screw the original extractor to the end of the bar for a pattern.
I put that bar in a rotary index head on a Bridgeport,so the length of the bar was horizontal,and aligned with the "Y" axis on the mahchine.
Then I just used my eyeball and a loupe to bring a corner or other geometry of an end mill as close to that extractor as I could get without touching it. Within .002. I'd make a cut the length of the bar,to the chuck on the rotary index tool .
(YuasaAccudex,a rotary table with a chuck and 90 deg base)
Then I'd turn the fixture a bit,ane eyeball another cut.I worked all around the original extractor that way,and made a bar that had about 6 inches of the outside shape of a rolling block extractor. Easy.Just eyeballing off a pattern part..Then I filed/stoned the cutter marks down on the outside to smooth it up.
Now,stand it up vertical and use a slotting saw to slice them off,but wait!!. Useabout a 5/32 thick saw,and use the thickness of the kerf to leave the stock standing for the extractor hook! In other words,don't cut all the way through with the slotting saw. You can switch to a thin one,.040 or so,to make the final "slice off"
Made really nice rotary extractors that way! 8620 steel is a great choice. A lot of modern receivers have been made of it. It can be case hardened,too.
If you look to a mold supply outfit like DME,you can get Core Pins and Ejector pins. I find both handy.
The steel is H-13 hotwork tool steel. These pins are hardened and ground. They have heads on them.You can get them hard,but machinable.
I made some real nice reverse bushings for a 1911 that needed a thick head.
The ejector pins are H-13 steel,softer,tough core but nitride very hard case,I have made rolling block pins out of those.