OP is sizing before powder coating. There is no need for that. I always powder coat before sizing. I've even cast, powder coated and sized on the same day even though that's probably frowned upon by some.
Powder coating makes the bullets "glide" through the sizer. Even 3-4 mil oversized bullets go through the sizer with ease. If you get upwards of 6-8 mils over the sizer, you risk scraping the powder coat off the bullets but dropped bullets 1-2 mils over the sizer with another 2-3 mils of of powder coat have never been a problem for me.