Hello all. I just picked up my M&P 15-22 today so I haven't had a chance to fire it yet but I saw this thread about ammo so I thought I'd post what my owners manual says about this.

I'll quote from the manual:
"Through our testing, Smith & Wesson has found that there are several brands and types of .22LR ammunition that do not perform consistently or reliably. Consequently, Smith & Wesson DOES NOT RECOMMEND that the following brands or types of .22LR ammunition be used in your M&P 15-22."

Remington Golden Bullet
Remington Target 22
Remington Thunderbolt
Winchester Wildcat
Any and all sub-sonic brands and types.

Also if you have the Performance Center Model it is equipped with a .22LR Lanley semi-auto match chamber which does not accommodate CCI Stinger brand ammunition. WARNING: Never use CCI .22LR Stinger brand ammunition in your M&P 15-22 Performance Center Model Rifle.

OK on to what they DO recommend.

"Based on the design and action of the M&P 15-22, Smith & Wesson recommends that you use the following brands and types of .22LR ammunition for optimal performance in your M&P 15-22 rifle".

CCI Standard Velocity
CCI Mini-Mag
Aguila Super Extra Std. Velocity
Aguila Super Extra High Velocity
Federal American Eagle
Federal GameShock
Winchester Super-X High Velocity

Sorry for the long post but I thought it might be a help to those wondering about what ammo to use.