Some more pics:

This photo is especially interesting - it looks like .30 Super is nearly as thin as 5.7x28, which really speaks well for overall mag capacity. 

Patent on the 8mm Super, before it was rebranded as the 30 SC:

https://patentimages.storage.googleapis.com/7e/27/f8/36daa7966d0382/US20210223009A1.pdf

And some rough Quickload estimates done on another forum:

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/16810359/re-30-super-carry#Post16810359

A nice look at 30 SC vs 9mm; you really can see how much narrower it is.

What's the main appeal of 380? I don't see the benefit over 9mm

smg762 said:

What's the main appeal of 380? I don't see the benefit over 9mm

Simpler (often direct blowback), cheaper and more compact pistols than for 9x19.  Often used for a small backup gun or a "Ladies pistol."   Smaller diameter cartridges were often derided as "mouse guns."

All of what nincomp said plus less recoil.

Obviously a 9mm is much more powerful than a .380 which is also called a 9 X17 mm. 

But imagine firing a 9mm in something as small as a Ruger LCP? Even with .380 it is pretty snappy. 

Realistically I doubt they could get a 9mm LCP. Whole pistol is 10.6oz, with a 0.75” thick slide - which is what makes .380 attractive.it’s the largest caliber that can fit in these diminutive pocket pistols.

They could scale up the Ruger LCP .380 to 9mm. It wouldn't be much fun to shoot and would be a lot to handle.

They have scaled it up, I believe it’s the LC9. It’s substantially thicker abd heavier relative to the LCP