Rolf - how much case length are you losing if using 57mm brass? You say, "are much to short" - that means overall case length. I'm curious is all.

To my way of thinking, losing .020" or so is about perfect - you'll never have to trim them to length, just even up the mouths if necessary and have at it.

Here's my 8mm to 9.3mm case changs. Note the first necked up case, is merely a new 8 X 57 case necked up to hold a .366" bullet. Note the difference in height between it's shoulder and the shoulder in the case that actually fits my chamber the fireformed case.

No annealing at any time during this process. Those wo say it cannot be done, have not use the proper equipment or havne't tried it.

I just measured a fireformed case at 2"215". I then checked the OAL "Trim to Length" suggested for an 8X57mm chamber and it's 2.235". That means my brass shortened .020" form the suggested brass length - which is OK by me. It will never need trimming since it didn't stretch at the web when fireformes. Since the rifle continues to shoot into 1/2" or less at 100 meters, I think it's probably OK using that brass. The slightly short necks will not cause the barrel to wear excessively in my nor my daughter's lifetimes.

The dies I use - single pass through lubed 8mm case neck - no annealing necessary. Necking 9.3x57 brass or even 8x57 brass out for the 10.75 should be little different.
The FL die is used to set teh shoulder in the correct postition - by feel. Neck it a bit, then try to chamber - stop placing the new shoulder when it will chamber with 'some' force. When fired, they will extract perfectly formed without stretching.

Use this system with any brass you use so that your shoulders are full size due to being formed by your sizing die.