For Christmas my wife bought an M&P10 Sport 16". Me being the implusive over acheiver I am, I bought parts Handguards Furniture Muzzle break etc before ever running any rounds through it.
Well I get all the new parts installed. Take it to the range and every round required me to rack the Charging handle. The Bolt was short stroking and the ejection was super weak. I suspected maybe an alignment issue with Gas Block etc. Pulled the rifle apart, everything was spont on. Did some investigation the only material I could find regarding gas system specs was that the Gas Port in the barrel was .068". Some suspect these rifles are under gassed. I compared the factory port to a 5/64" bit (.0781) and the gas port was much smaller than the 5/64 bit. Anyway for the heck of it I bumped it up to a 5/64". Took it out and the weapon acted flawless. Ate everything I put through it did not feel over gassed. Pretty sure this resolved my issue. Based on the charts Ive read .070"-.086" some charts are a tad smaller in specs for mid length gas port holes for a 16". 5/64 splits the difference. So far so good. I do plan on adding an adjsutable gas block and tuning it just for the hell of it.