.38 S&W Caliber Conversion Kit for Dillon RL-550B

[ezypikns]

I'm going to start reloading (gently) some .38 S&W for an old top-break revolver. I noticed that Dillon has a caliber conversion kit for .38 S&W, so I promptly ordered one.
I know that the .38 S&W bullet is a couple of thousandths bigger than .38 special, so I'm wondering why you would need a special caliber conversion. How come you couldn't use a .38 special kit?
I do know that .38 S&W cases are considerably shorter than .38 special. Maybe the Dillon .38 S&W shellplate makes up for that difference. As I said, I've already ordered the conversion kit. Just wondering.

 

[Jim Watson]

.38 S&W has a larger case o.d. than Special; .384" vs .379" as I recall.
Is a Dillon Special shellplate tight enough for .005" to matter? They think so.
.38 S&W is considerably shorter, the powder funnel is surely longer. Larger diameter? I dunno. If you don't cast your own .361" bullets are going to be hard to find. .358" shoots well enough for anything I use a .38 S&W for. (CAS Pocket Pistol and Derringer.)