Inside reaming or outside turning may be necessary if using '06-type cases and may end up with a do-nut inside where the old shoulder/neck junction is.

Here's a reply on another forum about this round from a fellow with one or more of them.

:I ordered a 100 case lot of 7x57mm brass to use with my M1904s. Rather than purchase expensive reloading dies, I bought a set of used 6.5x55mm Swedish dies at a gun show and use the FL die to neck size my cases. You can size the necks directly to 6.5 without any issues and without any intermediate steps.

I leave a very small artificial shoulder at the base of the neck of the 7x57mm brass for the very first firing. It requires a tiny bit of extra effort to close the bolt. The mini shoulder holds the cartridge head snug up against the bolt face for the first firing, which ensures that there is the absolute minimal stretching of the case during firing. This helps prolong case life along with periodic annealing. I use light loads in all of the WWI vintage rifles from the Collection that I shoot since I only use them to punch paper.

Both of my Vergueiros are extremely accurate and the 6.5x58mm would be an excellent cartridge for deer or wild pigs."