9x23 vs .356TSW

Case length. 9x23 is, well, 23mm long; TSW is about a 9x21.5. Not interchangeable.

The Brass...one is made to accually take the pressure of 50K CUP and the other isn't.

FWIW,
In 1996 I purchased a matching set of S&W Performance Center .356 TSW guns, straight out of the box neither gun was 100% reliable with the Federal factory .356TSW 147gr loadings and the compact model would often fail to eject and feed with the round becoming wedged in the ejection port.

I was finaly able to test the .356 round in gelatin and the Hydrashock bullet did not expand. The bullet traveled 24", exited the blocks and was stopped on the backstop.
I then spent a considerable amount of time and made 30" blocks and tested the rounds in bare unobstructed gelatin.

All five of the tested .356 147gr Federal Hydrashock rounds failed to expand and penetrated 26 to 18.5".
I also tested the FMJ target round and it penetrated a staggering 34" of bare 10% gelatin.

Velocity was much lower than quoted and averaged 1,075fps.

The Corbon 124gr 356TSW load was also not relaible. They used pistol primers in a round that needed rifle primers. They did hit 1400+fps but the primer flow kept the round from working in factory form.