A stovepipe is technically an empty case sticking out of the ejection port. Is this what your stoppage looks like?

This is a Failure to Eject. First suspect is the extractor. Dirt and crud will keep it from holding the case to the bolt face until the case strikes the ejector.

Ejector is the second suspect. Early M&P15-22 rifles had theirs slightly out of place. Good photo essays regarding the simple fix. Probably a video too.

If you have a live round sticking out it a Failure to Feed and is magazine related. Could be loading error. Could be too many rounds in the magazine. They won't hold 25 unless the rounds stagger. Part of proper loading the magazine is checking for stagger. If the 25th round is hard to insert leave it out and just shoot 24.

Staggered vs. not-Staggered:



-- Chuck