He is getting a solid indicator reading. However what is that reading representing?
Range rods only touch the bore in two places about two to three inches apart.
Again, assuming, its perfectly centered in perfectly fit bushings, the rod is representing a projection of the alignment of the two points in the bore that it is touching.
Like any of us that smith is getting the bore running as close as he can with the tools he has. I wont say it is or is not good enough, and i couldnt tell you what kind of accuracy he can obtain like that.
My problem with range rods is that you cant see any part of the bore that lies between or beyond those two points. Most chambers are about two inches long, and the bushing on the chamber reamer is going to ride the bore far in front of the reach of his range rod. Also if the face of the barrel isnt square with the bore, and completely burrless the range rod will reflect this. Its very common to indicate a range rod, pull it out, re insert it, and get a different reading.
Grizzly rods allow you to indicate any point along the bore thats within reach of the rod. They are about 12" long. They dont project the tolerance, its actually the opposite. The further in you go, you are actually only reading a fraction of what the tip is moving, but you can see any part of the bore over a large span, and a well fit bushing in a good cut bore will usually ride it pretty close.
This goes back to my question earlier.
Would you rather have 4" of a bore run within .0002" or 10" of a bore run within .0005"?
Maybe if we can start over it will clear up some of your questions.
First = If you use the bore of the barrel to align it, The bore must be true end to end, and the bore must be perfectly round and the lands and groves must be consistent with each other(The same height/depth. This is why a premium barrel must be used. If you start with a barrel that has poor straightness tolerances you will never get a true bore straightness, just an average of the worst/best of that bore.
Some Premium barrel makers list there straightness tolerance. I prefer the ones that have a Bore straightness of .0001 end to end. (At least I start with a true barrel that has a chance of being very good). Some will be better than that , but that is the maximum run out that will be excepted and shipped to the customer.
A barrel that starts out more (some have a rejection of .003 end to end, Not .0001) and it would be impossible to do a very good job or alignment. you might luck out and end up with a shooter but the odds are stacked against you.
Now assuming you have a barrel with a .0001 or better end to end TIR and you use a indicator rod
or any bore alignment device. Longer is always better (Just like site radius). also the tool has to fit the bore perfectly, no exceptions. if it doesn't contact "ALL " of the lands you are wasting your time with that tool.
The dial indicator should be at least a .0005 or better yet a .0001 indicator and preferably a last word type (They have a small range and have very little spring loading that could cause any deflection of the tool.
The term trash in trash out definitely applies when setting up a barrel for chambering. Good barrels, good tools, and knowledge of the best way to use them is a big start in getting a quality job. Last but not least is the craftsmanship and persistence in getting the best set up possible. all of this normally equals an accurate rifle.
I hope this helps. And thanks Barrelnut , for the kind words. I would like to think that all good smiths would try there best every time because they want to.
J E CUSTOM
PS: My experience has been that the more precise the tolerances throughout the build, The more forgiving the rifle is to different loads(It will shoot everything good, but when you do load development and find the best load, It will blow your socks off).
