You can start with adjusting the lips on the magazine & polishing the feed ramp, and there are stickies on here to show you how. also it may not like Winchester ammo so you use something different like blazer brass or federal. Plus the c-9 has somewhat of a break in of a couple hundred rounds or so but if you do the things I just mentioned it should be fine
with win its hit or miss. my c9 loves it. others seem to have problems with it. try some blazer or pmc 115 grain....mine loves that too. now that i think about it, my c9's eaten up every type of ammo ive tried in it.
I haven`t had any problems with Winchester white box ammo i shoot 100 rounds though my JHP 45 not one jam the only problem was. When i tried hollow point Winchester white box then it jammed nose up so i won`t shoot Winchester hollow point any more.