Small bolt face more accurate to build on for a 308

[James Jones]

I was able to get two actions from Brownells but both are small bolt face (.378") , one gun is gonna be a 223 and the other was gonna be a 308. Well in my efforts to find a new bolt with the larger bolt face a local smith stated that it would be better to use the 223 bolt face and open it up , his thinking is that you would be able to make the bolt face perfectly centered if indexed off of the bolt body when machined. it sounds pretty logical any of you builders out their care to comment on this?
How much would it cost to have the bolt face opened up from .378 to .473 if it were done when the actions was being trued anyway?

[chris matthews]

I don't feel that it would be more accurate. For the following reasons-
1. The chamber , if centered properly, holds the case, the bolt simply pushes the case foward into the shoulder, in effect wedging it into the chamber.
2. The bolt face must be bigger than the brass for different brands of brass and to allow the brass to "roll out" of the bolt during ejection. Due to this you can see why the bolt does not really have anything to do with holding the case centered, however it is important to have the bolt face square to bore.
But opening the bolt face is usually part of chambering and/or installation of a replacement extractor (Sako for example) runs about $80 for installation plus cost of the extractor. The feed lips will also need to be opened.
Another option is to find another bolt (Pacific Tool makes replacement Remmy bolts that can be fit to your action for a tight lock up)- see the bolt sleeving thread.