I would like to know how much should a guy reduce his load when using small federal mag primers in a 9mm? I don't have any small pistol primers except a brick of mag primers. I also have to seat the bullet a little deeper with powder coating. My bullet is a 120 gr that actually come out to 128 gr after powder coat. I have allot of unique powder and was thinking 3.6 gr for starters. I will be shooting this in a S&W M&P shield 2.0. What do you guys think?