Pinkerton: I have not had any problems using 9x23mm brass in my 38 Supers. I use them interchageably. Some 38 Super chambers need to be opened up that additional .2mm to be able to use the 9x23mm brass. 38 Super brass is semi-rimmed straight cased cartridge and early on the round was not noted for its accuracy until aftermarket barrel makers and then the gun makers themselves began chambering 38 Super barrels to headspace on the case mouth as with the 45 acp and the 9mm; then the caliber got some due for its accuracy capabilities. Then the 9x23 was introduced at the same power and pressure levels as the original 38 Super loadings.
The 38 Super has a bit of history. It was not the first American 38 automatic pistol round, the 38 Auto was. Both cases are dimentionally identical. The original 38 auto loadings fired a 130 gn 9mm bullet at 1280'/sec which is what todays 38 Super factory loads are usually rated at. When the 38 Super was first introduced, in order to avoid problems with the earlier 38 Colt autos, the 38 Auto was loaded down to about 1080'/sec and the 38 Super was loaded down to about 1280'/sec. Original 38 Super loads were at the same levels as the current 9x23mm Winchester.
I usually use a heavier recoil spring package in my 38 Supers - rather than the 16 lab recoil spring I prefer a 18-20 lb spring, with attendant firing pin and slide saftey spring, from Wolfe Springs in Ardmore, PA.
The 38 Super/9x23 runs just fine on a whole bunch of bullet weights and I use everything from 115 gn hps to 160 rn cast. I prefer SR4756 or H110 with the jacketed slugs in 115-125 gn range but favor Unique with the 125s. I have not used any of the AL powders in ages and cannot/should not comment on them. Sierra load data runs max loads of SR4756 to 9.6 gns with a 115 gn slug for 1550'/sec and 15.5 gns of H110 for 1450'/sec. My fun time plinkers with a 158/160 gn rn slug use 5-6 gns of Unique for 1050 - 1190'/sec. My max loads with a 125 gn jacketed slug usually use 7.7 gns of Unique for about 1425'/sec.
If your pistol does not like to extract 9x23s as reliably as the 38 Supers, then get yourself a 9mm extractor and change the old one out. Most gun makers today use a 9mm extractor claw in 38 Supers.
And, of course, you can always get a 9mm barrel and shoot surplus ammo, if the 9mm becomes surplus again.....
The 38 Super is a excellent field round. I once duplicated a Col. Charles Askins loading with H110 and a 115 gn slug to take a Jaguar in South America that went near 200 lbs. I have used it for varmit and other smaller critters and although near the 357 mag in velocity with heavier cast slugs (158-160 gn) I would not use it for Whitetail beyond 25m with jacketed hp slugs. The 9x23mm Winchester/38 Super offerings are excellent defensive rounds; The 9x23 significantly surpasses 9x19mm loads and the 38 Super, whether factory loaded or handloaded is in the same category as the 9x23.
The IPSC shooters favored the 38 Super for years - many still do - and loadings for that sport are hot. There is a lot of information available on the net for this round. Have fun and enjoy.