There's another thread about crimp and velocity. Most are saying more crimp doesn't change powder burn or velocity. I thought more crimp would delay (how ever slight) the bullet exiting the case promoting powder burn. When doing magnum loads with 2400 powder I noticed much less powder residue after firing coated SWC's with a good roll crimp than the identical load but with plated RNFP (Xtreme) and a light roll crimp.
Anyway, as my stash of Xtreme bullets for revolvers dwindles down I'll most likely order coated to replace them. I find them a bit "less fussy" to load.