Handloading Hornady FTX/Lil Gun max load

[Demi-human]

BTW...is there a formula out there that can used to come up with at least a ballpark idea of pressure generated based on powder quantity and bullet weight? I know the only way to measure pressure exactly is with a test barrel, but it would be nice to have an idea if a particular load is 10,000 or 15,000 CUP's below what the gun was designed to handle.

Yes!
Sort of.
QuickLoad is a computer program that will predict pressures and velocities based on a number of specific measurements made of your chamber and brass and bullets, etc.
But it is not infallible. It will get you close.
And is maybe a bit expensive for only one firearm.