I also seat first....then crimp as a separate operation. Also using RCBS cowboy dies for my 45 colt.
I know some people seat and crimp at the same time, but I am kind of fussy, and I have the time, so I do it the way I want. The crimp die is backed off while I seat the bullets, after I seat them all, I back off the bullet seat, and then crimp them all. I think my ammo is a little higher quality this way. 45 Colt is my favorite caliber, so I don't mind taking my time.