amheck,
I've have been reloading for over forty years, but I'm constantly learning how much I don't know about reloading.
You have to get some reloading manuals and read them before you start. My favorites are The Lyman Pistol and revolver manual and Hodgdon's annual reloading manual (magazine size). A subscription to Handloader magazine would also be a good idea.
I crimp all my reloads in a Lee factory crimp die in a separate press after the bullet is seated and that works very well for me.
Tired of scrubbing lead form my barrels, I now usually load either coated bullets from Bayou, SNS Casting, X-treme, or Missouri Bullets (sometimes, X-treme has free shipping). Or plated bullets from Berry's (and Berry's has some nice ammo boxes with hinged covers). I believe that they all have 148 and 158 grain bullets. The 148 grain wad cutters have been around forever, make nice clean cut holes in the target and are usually loaded on the light side and very pleasant to shoot in a J frame S&W. I like a little more oomph behind my wadcutters and load them with 3.0 to 3.3 grains of Bullseye, but I didn't start out doing that. That's the magic of reloading your own bullets. You can make the load the way you like it. Berry's has a nice hollow base plated wad cutter, but it doesn't have a crimp groove, so I set the overall length to be the same as the coated bullets crimped in the crimp groove.
The 158 grain semi wad cutters are probably better for longer range or hunting type shots, but I doubt you'll be doing much of that with a 642.
If I wanted a 38 special self defense load, I'd probably load a semi jacketed hollow or soft point bullet or Hornady XTP using +P load data. If you search this forum, you might find some threads on using wad cutters for self defense. The bottom line is usually that if you want absolute stopping performance, you need more power and/or mass.
For what it's worth, I wouldn't want to be shot with any of my 38 special loads.
I'm sorry for the long post, but it's late and after my nightly glass of wine, I start rambling.
Keep asking questions; that's always good. And good luck with your new press.
George
PS: The best source I've found for jacketed bullets is:
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