A 6.5X54mm Mannlicher-Schoenauer FL Resizing Die, used with a .303 or .30-40 shell holder, can be used for final sizing.

.303 British or .30-40 Krag brass will both work to make 6.5 Dutch ammo.

IIRC - I used .308 and 7mm Mauser  FL Sizing Dies (with decapping pin removed) to gradually size down neck. The length of the 'reworked' neck, before final trimming, was truly remarkable. It took a lot of cranks, on my Lyman case trimmer, to get the case to correct OAL!

I used 6.5X54 M-S reloading data.

Caution - I initially tried simply putting Dutch powder charge and projectile from a military round into one of my reformed .303 British cases. TOO HOT!

The first round, I fired, expanded the primer pocket. When the case was ejected, the boxer primer fell out of the case.

I did use the Dutch projectiles with IMR powders and M-S loads, without problem and good accuracy.

It's a nice cartridge and was popular in Scotland after WW1 for Highland Deer hunting.