Joe, yes sir this will shoot both 5.56 & .223 >>> smith-wesson.com/firearms/archive-model-mp15-ps .....Have a great day!

Yes as others sat .223 only shoots .223, so the decision is obvious.

Yes as the others said, .223 only shoots .223, but .556 shoots both. So obviously get .556 no matter what!

Yes, this is a 5.56 so it can shoot both 223 rem, and 5.56mm. barrels stamped 223rem can only shoot 223rem but 5.56 stamped barrels can shoot both. Hope this helps.

Joseph, the M&P rifles can fire both 5.56 & .223 no issue. The barrel is actually stamped 5.56NATO. Cheers and stay safe!

Yes it is fine with both 223 and 5.56 see **** from S&W spec sheet SPECIFICATIONS
SKU: 811022
Model: ARCHIVE: Model M&P15 PS
*******Caliber: 5.56mm NATO/.223
Capacity:
Barrel Length: 16"
Overall Length: 35.0"
Action: Semi-Auto Blow Back
Stock: Collapsible 6-position
Barrel Material: 4140 Steel
Barrel Twist: 1 in 9"
smith-wesson.com/firearms/archive-model-mp15-ps