When I had a 1903 Springfield rebored to 9.3x62 by JES, I grabbed a new Hornady New Dimension FL sizing die off eBay for $15 while I was searching for a full set. It has turned out to be one of the most precise and accurate dies I ever owned. I very carefully measure the effects of all my sizing dies on my brass, testing for runout. These are near perfect. The next one off the line might not have been, who knows.
That said,
The shoulder being further forward on the 9.3 than the '06 is a big deal. You can't just neck it up.
Rex
Here is a 286 Privi seated to touch the lands. As you can see it has plenty of room to seat further out.
Next to the Privi is a 286 Partition, it could also be used for fire forming, kinda wasteful though...
As for the 30- 06 brass base being smaller, it's a one time deal, your 9.3 die will not size it back down, leading to repeated stress.
This pic should remove any doubt as to whether I am making things up
![[Linked Image from i.postimg.cc]](https://i.postimg.cc/qqFP4yd6/DSCF1279.jpg)
