The answer is pretty simple.
The .38 Short Colt.
The .38 Short colt is essentially the grandfather to the .38 Special and chambers in any .38 or .357 Magnum revolver. It is essentially a .38 Special, cut to 9mm length. The commercial version I load are loaded with a 125 grain polymer projectile and are low recoil loads. As an added bonus, due to their short length they eject super easy out of revolver with short ejector rods like the typical J frame.
They are quite popular with J Frame/Chiefs Special shooters who like to shoot those style guns but don't like the recoil normally associated with shooting them. In a medium frame revolver there is hardly any more recoil than a rimfire load.
Here is a pic of .38 Specials compared to .38 Short Colts:
Here is a link to the Short Colts on the web store if you want some:
https://www.lostriverammocompany.com/product/38-Short-Colt-125-Grn-Poly-Coat-TC-Flat-Point-100-RNDI made a bunch about a week ago, and most have already sold.