I have been reloading for sixty years (as well as casting my own bullets).

I have LONG been a fan of a separate crimp die. The issue is not quite as simple as some would suggest (not pointing fingers at any of us, of course). If you use a bullet with a long, tapered crimp groove (genuine Keith designs are good examples) you can use a three die set to good effect crimping as you seat the bullet. However, MANY bullet designs without that long tapered crimp group will push lead ahead of the bullet as you try to seat and crimp at the same time.

Back in the day, I was quite active in PPC shooting when revolvers ruled the roost. I had access to a Ransom Rest and also many fellow club members loaned me their revolvers to run on the Rest with a variety of loading techniques. We shot wadcutters on every stage except the speed loading stage (for that one we shot round nose standard bullets for obvious reasons).

I discovered the the four die set was VERY desirable as it allowed me to seat with the seating die, then crimp with the 4th die insuring that no lead was pushed ahead of the case mouth to cause leading, accuracy issues or feeding issues with auto pistols. I also discovered, to my satisfaction that I got better results with the wadcutters when a taper crimp was employed. I learned to use JUST enough taper crimp to retain the bullets from moving forward from recoil delivered the bullet to the revolver with minimal damage going from the case to cylinder throats to barrel forcing cone. This gave more consistent accuracy. However, in fairness, I admit that you can load excellent wadcutter ammunition with a light roll crimp. Just don't overdo the crimp whether roll or taper.

The taper crimp die is more forgiving if you are using mixed brass that has not been trimmed. Consistent roll crimping requires brass to be of the same length to get good, accuracy results (otherwise you will get inconsistent crimps).

Later, when loading for the Smith Model 52 auto pistol, I learned that this only used flush mounted wadcutters. As I said above, I cast most of my own bullets but ran tests with hollow base wadcutters of various brands as well as cast dbl ended wadcutters. I also tested various brands of .38 Special match ammo at the same time.

Ed Harris has written extensively on loading .38 Special ammo (he was an NRA Technician and also a developmental engineer with Ruger). It would pay you to read what he has to say regarding powder charges and .38 wadcutters.

Ed Harris: Casting and reloading the .38/.357 | Reloading, Ammunition | GrantCunningham.com

I have two Dillon 550B's set up to load (one for small primers and one for large primers) as well as a Lee Classic Cast Turret (four hole turret) for small batches. The Lee allows you to change calibers in seconds and if I have less than 200 rounds to load, the Lee will do it in an hour including set up time.

As a matter of fact, I recommend the Lee to any mechanically minded beginner that wants to load for handguns. He can load as a single stage press until he gets accustomed to the machine, then work up to 150-200 rounds per hour. It is a great press at a great price.

Later, when and if his needs expand, he can buy a Dillon while keeping the Lee for small runs, as I do.

FWIW
Dale53