I wonder if either 32 S&W or 32 S&W long would reach full velocity when shot from a 32-20 gun.
Best try the test with a gun really chambered for these two cartridges to get valid info.
I remember reading a test by a guy who shot 22lr out of a 22WMR revolver.
Sure it shot the 22lr, but the measured velocity was way low and, it varied all over the place from round to round.
I'm thinking you are correct. The 3in. IJ .32S&W penetrated a little deeper than the .32S&W did in the 6 in. 32-20. I don't have a pistol that is chambered in .32L so I can't make that comparison. Larry