Fire forming without a projectile.

[Downunder]

Hey folks, I have a couple a hundred .17HH cases that had the shoulder bumped back to SAAMI specs. I want to fire form them to my chamber then bump them only a thou or 2 (which is .090 longer than SAAMI.
Consumables are getting hard to come by round here and projectiles have gone up 30%, I’ve never fire formed without a projectile but have read over the years of people using fast burning powders and wads but know nothing about it.
I’d reckon it would take a few firings given it takes up to 3 firings when fire forming fully loaded factory brass.

Any advice is appreciated.

Regards,


Tony