rocky mtn bill,
You are certainly entitled to do what ever you want with your own property, but since you asked for our advice, here is mine. I have a couple rifles that were "born" 8.15x46R and are now chambered for something else( one also lined). I have another that had original markings ground off so original caliber is unknown, but was re-bored and re-chambered( both operations oversize so intended caliber cases split over 50% of the time). Since they had all been "messed up" , I got them cheap because the owners didn't want to see them any more. xausa is correct about the bullet in the neck test. I usually limited re-sizing jacketed bullets to .005" once, so I appreciate the 3 x .003" hint. I often see rifles with even a tighter barrel than yours ( down to .3125") and still intended to use the "standard" bullet. The 8.15 bullets were usually shown as .324" but the main body was .318" with the extra diameter a "stop ring" which allowed loading at the range by seating the bullets by hand without sizing and still seating all bullets to the same depth. My advice is to shoot the rifle "as is" using cases made from 30-30 cases, sized, trimmed, adjust rim diameter and thickness; with bullets in accordance with xausa's advice. You didn't say what type rifle you have, but if it is one of the "tip up" single shots with a single locking lug, they were never offered in 8x57 IR. They were intended for lower pressure cartridges up to 9.3x72R. If you are "bound and determined" to re-chamber it, you would be limited to 8x57R/360 or 8x58R S&S( the S&S may not cleanup the old chamber). In the end, you wouldn't gain much, donor brass will be more difficult, bullets would be the same , you would have to find or make a reamer, and everybody would fuss about messing up the rifle ( it's yours but they will still fuss). You asked, so there it is. If you decide to do it anyway, I will take it off your hands cheap, when you get sick of it.