45acp brass isn't strong or safe enough to run at 28,000 psi. period.
How a gun is built doesn't change that fact.
This is absolutely incorrect. The fact is, that how a gun is built is the single most important factor in what amount of pressure it can handle.
It isn't that the .45ACP case is not strong enough to be safe at 28Kpsi, its that the majority of guns made for the .45acp are not made to support the brass well enough to allow it to safely run at 28Kpsi.
While I haven't personally done it, because I've never had a reason to try, I'm absolutely certain I could load .45acp brass to 28Kpsi (or likely more) and safely fire it from my new model Ruger Blackhawk convertible. The gun will take the "Ruger Only" .45 Colt loads that rival .44 Magnum, I'm positive the ACP cylinder would handle 28Kpsi acp loads.
However a tilt barrel semi auto would probably not handle those loads well, and might even be unsafe.
The classic example of it being the GUN, not the BRASS is the .45-70.
The Trap Door Springfield rifles are weak, strong enough for black powder but not beyond those pressures. Later, stronger rifle designs allow the .45-70 to be loaded to much higher pressures safely, while using the same brass case as the low pressure BP level loads.
The same case.
Its the gun, specifically how it supports the brass and how it locks up, not the brass case itself that determines what pressure level is safe.