It should be Stock Service Pistol Division (SSP). But it all depends on the internal workings if the striker is cocked and released or just released. I believe the M&P is a cocking action striker gun. If the striker is just released than it falls into the Enhanced Service Pistol Division (ESP). M&P guns where not out when I shot IDPA, Now I shoot USPSA and the M&P is a Production Class gun. IMO IDPA has way too complex in its rules and procedures to be a fun sport.
"They say you can't use a rifle or shotgun indoors because a bad guy will grab the barrel. Yeah? Well, he better hang on, 'cause I'm gonna light him up and it will definitely be an "E" ticket ride."
"Make (your attacker) advance through a wall of bullets. I may get killed with my own gun, but hes gonna have to beat me to death with it, 'cause it's going to be empty."
Clint Smith, Thunder Ranch