This is probably not very important but I once read that on all military Mauser rifle the rails were made for the exact cartridge they were intended for. That is, the width and taper was exactly planned for the diameter and taper of the cartridge the action was chambered for for the best possible feeding. Anyway, I had a 1909 Argentine Mauser fixed up and decided to go with a cartridge with a similar body taper to the original cartridge. I decided on a 7X57, but a 6.5X57, 8X57 or 6MM Rem would have a similar taper and be the right length. The .243, .260, .308 and .358 are a little more blown out. Also, my gunsmith said that most of the chamber reamers for the 7X57 do not have the long freebore to accommodate the 175-grain military bullets. Jump to the lands is a short distance with bullets pointed bullets in the 140-grain weight range. And they pretty much use all the magazine length. I used a Shilen pre-chambered and threaded barrel and it did not take long for the gunsmith to get it fitted up to the action. Also, I had the gunsmith cut and re-weld the bolt rather than bend it as he would have done. I could use lower scope mounts that way.