Federal premium law enforcement tactical 124 grain hst hp is probably the best in my opinion. That's what I carry. Item# p9hst1.
Out of curiosity, why 124 vs. 115 or 147?
Federal premium law enforcement tactical 124 grain hst hp is probably the best in my opinion. That's what I carry. Item# p9hst1.
The newer M&P's have a 1 in 10 twist. All the guys I shoot IDPA and USPSA with use 147 grain ammo, which gives the tightest 25 yard groups. The slower the twist, the lighter the bullet. Older M&P's used 1 in 18.75 and shot better with 115 grain ammo.
For self defense, I carry Federal HST, 147 grain +P.
Here are some penetration and expansion test results with photos:
https://pistol-forum.com/showthread.php?4337-Service-Caliber-Handgun-Duty-and-Self-Defense-Ammo
Handgun Self-Defense Ammunition - Ballistic Testing Data