sounds like you're loading lead. i had to flare my case mouth a lil extra on my lead .40 loads as well. not too much, but 'just enough' heh.
also, if you're loading a powder thrower (rather than scale & funnels), particularly if you're using a progressive press, make sure the powder hopper is high enough that the brass alignment cone doesn't re-crimp the mouth, but not too low as to not fully actuate the hopper/thrower.
also, with lead, you'll always get a bit of 'dust' over the long haul... just clean up with an oil / dry-lube damp paper towel every so often (every batch or two, depending on if anyone might disturb your reloading area or not... lead is bad for ya and all)