There is nothing unique about variations in the size of fired brass in handguns. The same thing occurs in rifles and shotguns.
There will be a difference in the case expansion of a standard 9mm or 40 S&W load and a +P+ fired in the same firearm, small but measurable.
Measurement of case head expansion was the method used by noted reloading guru Ken Waters for the NRA to determine when he had reached the upper limit of pressure when working up reloads.
Another factor is variations in chamber dimensions. There is industry standards that chambers are required to fall within; regardless of whither it is a Glock, H&K, S&W, SIG, or master blaster.
I have two Winchester M-70 Classic rifles in 270 Winchester calibers. The chambers are very different. A cartridge case fired in rifle “A” can be neck sized, reloaded and re-fired in rifle “A” many times and never need to be full length sized.
Insert the cartridge in rifle “B” and you can’t even close the bolt on it.
I have been told that the reason is that gun manufacturers specify to die makers for a reamer to have certain exact dimensions. A new chamber reamer will drill a “Larger Hole” than one that has reamed an untold number of chambers. They use these reamers as long as they ream chambers within an industry standard tolerance.
To help reloader’s with the created dilemma, I know that both Redding and RCBS manufacture SB (Small Base) rifle dies for those with chambers on the small side. I have two 270 Winchester die sets, one standard for rifle “A” and a “SB” set for rifle “B”.
I use Glock 9mm & 40 S&W, load with Dillon 550B reloader and have no problems. Well, occasionally I run out of powder, primers, or bullets.
9mm in excess of 80,000 rounds. 40,000+ in a single Glock19.
40 S&W in excess of 12,000 rounds in a glock 23.