[How do I?] Need Advice on Machining a Part

I make many of these type of parts out of 01 drill rod which can be further hardened if needed. You could bore the center with a 0.250 drill, or if you need to be slightly over, I often use a 0.251" reamer for final sizing. For the 0.268 hole you can purchase a 6.8 mm drill for less than $10, this will give you a 0.2677 hole which most likely will come out to 0.268" when all is said and done. If you need to be very precise or a square transition, you could mill a cutter/reamer out of 01 steel (or some type of tool steel) that would be hardened to get the precise final dimension, otherwise use some form of hone/grinding compound used with a round pin for a final fit. On the external thread, I use adjustable round dies for final thread sizing, I can adjust the cut depth for a very precise (almost zero tolerance fit). You may want to do some form of surface hardening if this gets a lot of repetitive wear.
http://www.ebay.com/itm/Hertel-2677-6-8MM-SE-Drill-NEW-in-Package-QTY-1-Overstock-/182186024779
http://www.ebay.com/itm/New-Garr-Tool-End-Mill-6-8-MM-Micrograin-/172707840136
 
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Began a sure to be troublesome part today, it features a 1.563" + .0005 -.0000 X 6" deep bore (with a flat bottom) finished after welding in a 2 1/2" Dia X 6.718" long 304 stainless round, a flange is welded near one end leaving 1" to hold it in the chuck after welding, this will end in tears I suspect.
 
I have been reloading for 35 years and have never seen a part like that.
I would first ask some questions of the bro in law, such as, (1) can you give me the other parts and cartridge components that will contact it and (2) what finish is needed inside the tube? Iffen a smooth finish is needed inside, I would buy appropriate chucking reamers.


No part of a 7mm-08 cartridge would fit inside it.
 
Apparently parts can be interchanged between a 7mm mag and a 243.
At this point I/we have not moved forward with the project. A small investment is required for a tap and threading die, possibly reamer or two.
 
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