If you go to the bottom of the CCI stinger page, in red it specifically states "Use only in firearms having standard ANSI sporting barrel/chamber dimensions."

CCI Ammunition - Product Detail

I posted a photo link above that shows the difference in their measurements. Laney is just the company that makes this particular type of Match Chamber. I haven't been able to find anything specific about the ones in the M& 15-22's on their site, but you may be able to contact them and ask about it.

here is a link for all of the M&P 15-22 models S&W has available. Note, the only model with the Laney Chamber (Performance Model) is the A1 Style Comp version:

M&P15-22<br>.22 LR - Smith & Wesson

If you are running stingers through this model, then ultimately you are going to be prone to more jams and probably wont do the chamber too good in the long run.

The model with the magpuls stock is this model here: Product: Model M&P15-22 MOE Rifle - Magpul Sights, Stock and Grip

That model has the standard ANSI sporting barrel/chamber dimensions that will accommodate the longer size of the CCI Stingers