I was at Walmart and saw some 100 round boxes of .223 Rem Federal FMJ 55 grain ammo as well as 150 round boxes of 5.56 American Eagle Ammo. I'm New to the M&P... Any issues with this ammo? Thought I'd ask prior to purchasing a box or two Thanks guys!!

Federal and American Eagle are the same Company and do produce very high quality ammo! Just use what your rifle is actually chambered for. While some rifles will feed both the .223 and 5.56 interchangeably, some will not and will only function properly with what is stamped in the rifles barrel. I don't own an M&P and so I am not familiar with that particular rifle. You could always call the manufacturer to make sure.

I have used both the Federal and AE rounds in my AR. Check your chamber size before using the 5.56 AE rounds. If your barrel / lower is stamped 5.56 NATO you're good to go.

Also, the AE rounds will more than likely have crimped primer pockets like military rounds. If you reload these will have to be swagged or ground out before re-priming.

Had good results with both rounds tho'. Enjoy.