Ted, I like you bringing up about working with the older generation of machinist and what they bring to the table. What is being taught in schools now a days doesn’t even compare to what they taught in the past and the tooling/machining knowledge is being lost in my opinion.

A new rifle manufacturer is asking us and a button barrel maker to supply them with for the most part finished barrels. They want to offer both types. The chamber spec is a SAAMI min spec chamber. The headspace tolerance on the print is -.001” to +.001”. Which is a total of .002”. Even if you would check a barrel from the same maker and theoretically speaking the very same reamer was used and now throw in receiver and bolt tolerances it would possibly appear that one chamber is tighter than the other but it might not necessarily be the case. They might also be spec the headspace that way so when they go to put the barrel onto the receiver if the headspace is too tight they can go in with they’re reamer/tool and touch the chamber up and set the headspace. Which in our case we have no control over what reamer/tool they are using and by adding another tool and set up to the mix how it cuts and what the final dimensions end up being.

Between the receiver and bolt and barrel tolerances at times you are stacking the dimensions. Sometimes this works and sometimes it works against you. Even on custom actions or lets call it guns I’ve seen plenty of instances where they say that the firearm will accept a drop in barrel made to a given spec and it doesn’t. That’s why I say the best fit is still when you fit the barrel to the action on a individual bases.