I'm going to add a solid +1 to what Rick K said!
The factory crimp die is VERY good, and is worth using - especially if you seat the bullet, THEN crimp which is always best.
ALWAYS.
Think of it like this. With a crimp/seat die, While you (and your press
) are seating the bullet those last few thousandths of an inch, here comes the crimp portion of the die squeezing the case to where it de-forms a slight part of the bullet, because it isn't quite yet seated. In other words, you may WANT to crimp in the crimp groove provided on the bullet, but by seating and crimping on the same die, you cause the brass to dig into the side of the bullet, sometimes creating a "scraped flat" mini portion, which Should be filled out.
Now ... having said that, will that cause you problems for CAS shooting? In ammo used for revolver shooting: probably not. Rifle? POSSIBLY not. But maybe ... And
certainly in longer range shooting, for instance - beyond 50 yds. But may be not. I don't want to find out, (I miss enough on my own) so I ALWAYS crimp in a separate operation. Not a problem on a 4-position turret or progressive or single-stage press, but it adds time. You gets whut ya pay for.
I KNOW that
thousands of loaders seat/crimp in one operation and do fine, in their opinion (I used to) but now that I KNOW the difference, I do things this way. Another advantage of the LEE factory crimp die is that it gives the whole case a last "squeeze" which will take out any bulge that may be created by a crimp that is too heavy - which is VERY easy to do if your case lengths vary. How many of us trim our PISTOL cases? Not many. Oh yeah, RIFLE rounds, of course, but usually, the pistol brass goes untrimmed from day one until "Trash Day." Or until a reloader notices the VERY tight crimps he's getting and realizes that his cases are .00sumthin'-or-other LONGER than when he set the crimp on his die.
Your mileage may vary.
Happy Trails!