Hi there, FWIW I would suggest that you stay away from any steel cased ammo like Maxx. I have 3 Smith & Wesson M&P's and they did not perform well with this kind. (1 Pro Series C.O.R.E 5", 1 Pro Series C.O.R.E. 4.25", and 1 M&P 9 4.25"). After about 50 rounds or so they would fail to feed (FTF) and fail to eject (FTE). This cost me about a minute in an IDPA match. I have never had any issues with brass or aluminum cases.