Ive shot my old vests with all kinds of rounds! A 40 or 45 center mass is gunna mess your day up and knock you back, giving time for that all important string of head shots!
I stopped carrying a 9mm on duty after shooting vests.... if it wasnt for the stain on the vest, you wouldnt know the round hit! On the other hand, the 40 cal 180 grain completely folded the vest around the round... the 45 200 grain knocked the backstop off the rail !!!