No this method does not re-size the brass. The ones that were fired from my gun still chamber and eject with no resistance, I did not try to chamber any of the hulls that I scrounged from the range however. I don't know yet if they will still fit after they are fired a second time. However, I have already built a sizing bushing from cold roll steel to use with the Lee Load All that I'm trying to convert and it squeezes them right back into tolorance. I don't really know since I don't have any experience with shot shell loading, but I'm thinking that the cases may last a bit longer if I only size when they stop fitting well.