I've always wondered how accurate my pistols are. Still haven't found anybody to shoot them good enough.
You'll never know unless you try. 21 ft. is too short.
I found out in a class that mine sucked, sadly the first time I shot it at 25 yards. Then, the trainer offered to shoot it on a break to verify - same thing, we both got vertically strung ~6" groups. Good way to waste $525 + travel costs when your pistol can't shoot at distance. That's what got me testing all mine.
As I have written and documented previously, the vast majority of full-size M&P9's I've shot have been equivalent to a typical stock 3rd gen 9mm Glock--both pistol types running 90-95 at 25 yds on an NRA B8 slow fire right out of the box. I have seen and shot a couple of M&P9's that offered extremely poor accuracy, with weird flyers making shotgun like patterns at 25 yds. I've also seen some Glocks (both 3rd and 4th gen) with major issues. However the Glocks are generally easier to fix and get running acceptably; infrequently some M&P9's seem to resist all efforts to make them shoot better.
Facts matter...Feelings Can Lie