I set up a Lee 9mm Makarov Factory Crimp Die (FCD) in the Lee APP's lower mount and placed the debulger's ram in the upper mount (using the shellholder that's normally in the lower mount).
I then fed cleaned, deprimed brass, head up, into the press and rammed a couple through the Makarov die. It was very difficult, so I lubed the remaining test shells. They "debulged" easier, but still with effort. It did go quickly, like most processes on the APP.
I then cleaned off the lube and loaded about 25 cartridges on my Dillon 550c, running them through the Dillon 9mm sizer on the first stage.
I could see exactly ZERO difference between the "debulged" reloads and a normally reloaded cartridge.
Neither my "normal" 9mm reloads nor the "debulged" 9mm reloads fit perfectly into my tight-tolerance case gage. You can see the rim of the 9mm slightly protruding above the stainless case gage below.
They do fit into a Lyman case gage. Looser tolerances, I guess.
That said, every 9mm reload I've ever made has functioned flawlessly in every 9mm gun I own.
In your opinion, does "debulging" help you make more perfecter 9mm ammo or is it a nonessential step? Personally, I don't think I'll debulge in the future.