I just purchased an M&P 9 and have had it out twice and believe it shoots low. Now, as I am new to handguns I am perfectly willing to accept that this may be caused in part, or entirety, by my technique but I've been Googling it anyway and do see some similar experiences from others. While doing this I see several mentions of heavier bullets hitting higher than lighter ones. I'm curious about what causes this. My guess is that larger bullets travel down the barrel slower so the barrel it beginning to rotate up before the bullet leaves the muzzle. The heavier, and slower, the bullet the her action has traveled through its reward travel and there is more barrel rotation resulting in a higher POI. Is that close to correct?
Your conjecture is correct.
If you're shooting consistently low — and not low-left, which indicates a fault in technique — switching to a heavier bullet will raise your impact point.
Another benefit of using a heavier bullet is that it will be somewhat more likely to stop within its, um, target, thereby delivering more fight-stopping energy to it.
Note: I use "further," rather than f*a*r*t*h*e*r, because this forum's program turns the latter word into a .
My pocket-size .45 semi-auto seems to hit close enough to where my aged memory says that a full-size 1911 does (in my hands).
Of course, I shoot against IPSC-style silhouettes, and not on bullseyes.
If I were strictly looking for precision, I'd probably find that the mini-pistol's short barrel, giving a bullet shorter dwell-time within it, makes the gun shoot a little bit lower than does the full-size pistol.
Since I almost always shoot 115 FMJ out of my M&P 9 Pro Series 4.25" at the range, I have never noticed any problems with this. But as Steve mentioned, you are correct in your assumption. A bullet is long gone out of a barrel before pretty much anything takes place in the gun (recoil, rearward travel of the slide). But there is a very small reaction that does affect the travel of a bullet. And that's all it takes to cause a heavier bullet to striker higher on a target than a lighter one might (there are some other factors at play here as well).
As for the M&P Shield, they are fine little guns. Perhaps one of the best choices in their category. For shorter barreled guns like this, you are better off with a lighter bullet with a higher velocity because there is less barrel length to maximize a bullet's acceleration from the burning powder. Something no heavier than a 124 grain 9mm load would be the better choice. Both Federal (their HST series) and their sister company, Speer (Gold Dot) make fine examples of 124 grain loads with both available in +P ratings.