I have been playing around with my lathe trying to make my own chambering reamers.I use the compound feed to get the taper, my milling atachment to make the flutes, and my dremel tool to releve the flutes and sharpen.So far I have only made a prototype that does not conform to the demensions of any known caliber. I tried it in a old 8mm mauser barrel and it cuts as well a the commercial ones that it have used.I can get case demensions from the loading manuals.My questions are how much larger should the chamber be? How much extra length is normal for the neck? How much extra diameter is needed in the neck to be sure of good bullet release?Is there some formula to determine the throat length or should I just measure the longest bullet that I intend to shoot?I used water hardening drill rod is there a better choice that can be hardened without special equipment?