Straight walled case, crimping while bullet seating?

[Bigeclipse]

I just got a Dillon 750xl press. I noticed most my die sets have the taper crimp with the seater die while dillons dies are setup with a separate die to crimp after the bullet has been seated. Is one way better than the other?

 

[entoptics]

I'd say that 2 steps is better for sure, but how much better? Not sure...

Crimping during seating means the crimp starts before the bullet is all the way down, so you're seating against the crimp to some degree. This can result in gouging the bullet a little, and also potentially leaving a "long" crimp, which is likely less secure/consistent. I think the effect is more pronounced for roll crimps.

Personally, if I had space on the tool head for it, I'd buy a Lee Factory Crimp Die and do it in two steps. That's what I do on my 550B for all pistol ammo. I'll set the seating die deep enough to mostly close up the flair, then it goes into the crimp die to finish.

 

[sedancowboy]

A two step process is much preferred. Because if done in one step it sometimes pushes lead up on the lip of the case mouth which changes the headspace, if you taper crimp after seating then you avoid this and have a clean mouth for your cartridge to headspace on.