When I FL size with a ball in place, I use the water soluble RCBS lube. I lube the inside of the necks with a cotton swab, being sure to coat a bit of the shoulder just below its junction with the neck. Where will the ball make first contact on its way out, right?
They size straight and smooth, even though there is more resistance with thicker necked brass. A hot soapy water bath with neck brushing, hot water rinse, a shot of compressed air and a short ride in a 250 degree oven and they're ready.
I've found that when I've gotta run a ball with more than a thousandth or two interference, short cuts and "no remove wonder lubes" don't get it done for me.
BTW, how do you get the Imperial out of the necks? Besides, if I treat one neck a given way, then they all get the same treatment. I want consistent seating and bullet release.
MM, have you tried just throwing them in corn cob media to remove the lube?
