Heres one of many trains of thought.
If your going to build an engine so that it's as friction free as we can make it with conventional methods, you start with the crankshaft bearing saddles and main caps. You line bore and/or line hone the cylinder case to get this feature straight and round.
The same argument can be made regarding reaming the raceway of the action. It gets it straight and round. It also requires a bolt of a different size once your done.
Next, you resurface the deck of the block where the heads bolt on. You register off of the main saddles that you made straight/round. This ensures the deck is flat, parallel, and square to the cylinder bores.
The same as facing the lugs abutments and the front of the receiver ring where the recoil lug purchases.
Onto boring the holes where the piston(s) go. Straight walls that are round, free of taper, and later honed to the appropriate surface finish. -Most anymore go a step further and torque plate hone the bores but that's another story.
Once again, strikingly similar in principle as cleaning up action threads. You ID bore to a specified diameter, then align/time your threading tool and remove any taper, concentricity, and roundness errors from the threads.
Now your done with the bulk of the process.
The point is, when you started your engine you began at the point of origin. When you accurize an action this way, your doing the same thing. The whole package datums off the receiver bore centerline.
I haven't felt the need to ream the receiver bore due to the added expense a customer is going to absorb by having to either buy a new bolt or have bushings installed on his existing bolt. Bushings are a complete waste of time IMO and I've seen them create more problems than they'll ever hope to solve. That said, we go to great lengths to ensure that our setup mandrels and bushings are laser straight and properly qualified at the beginning of our accurizing process. Just like any other reputable shop does.
You can slap a rebuild kit into a SBC and get lucky with a 200K engine that doesn't burn oil. It's done all the time. Some however insist on having a bit more work done in the interest of peace of mind or more power. Same is true with this whole receiver accurizing process. You might be fortunate and have a rifle that just bedazzles everyone. The idea is to ultimately instill confidence in yourself through your equipment so that you know where shots are going to go and off call fliers become a thing of the past. Accurizing, done well and combined with a complete package of well assembled, quality parts, goes a long way towards accomplishing this.
Guys who do this for a living and who have been doing it for a long time have one distinct advantage over others operating at the hobby level. When you do something over and over again, you get good at it and your opinions become more factual because of the broader level of experience you now possess.
Hope this helps.
