My rifles chamber won't accept the slightly larger dia head of the Swede 6.5 case, so I went to 8x57 brass which I had. I've used some 7x57 commercial brass also.

I use a cut down 6.5 Swede die set (Lee) for forming and loading, neck sizing only after the first firing. The shoulder fireforms to bit of a different angle from what the 6.5Swede FL die leaves it in sizing and forming. But I use the first process to just get a shoulder set into position well enough to feel some resistance when I close the bolt.

I must first run the 8x57 brass up into a 303Brit FL die (w/o decapper-expander). This in order to decrease the case diameter up at the shoulder and just below it.
It's an educated push into the die but easily done.
If I don't do this step first, the 8x57 brass (or any of these types I've tried) will be a touch to wide in that area and hit the side walls of the chamber giving a false headspace reading as you are pushing the shoulder back in the cut down 6.5Swede die.
I found that out with the first few rounds I made up.