[greener]

I've had an M&P9 for 5-6 weeks. I believe the pistol shoots low and need advice on adjusting elevation. Shooting low is defined as 5-6 ring of a 25-yard slow fire B-8 target at 15 yards. I can put it in the 9-10 ring by putting the front sight dot on the target and having the bottom of the dot tangent to the two rear dots. I haven't ruled out shooter problems, but two other shooters put the rounds low today. The other reasons I think some of the problem may be the pistol is that I do not have that problem with my 22A, MKIII Hunter and Single Six. I also fired another 9mm today and put two rounds together 1 o'clock in the 9-10 ring and third in the X. That was the only three rounds fired from that pistol and the third round was consciously lowering POI.



My first thoughts are to send it back to S&W and let them have a look at the pistol. I've also thought about taking a file to the front sight to "fix" the problem and then look for a sight with that height. I haven't found an adjustable rear sight, which would, in my opinion, be the best solution. None of this shooting has been from a rest, since the range doesn't allow shooting from rests on that particular part.



I'd appreciate any suggestions on how to go about fixing the problem.

 

[matt7184]

What weight ammo do you use? If you are using try 115gr try some 147 gr and it should hit where you want it.

 

[greener]

I've been using 115gr. Typical mv's for 115gr are 1150-1250 fps. Typical mv's for 147 seems to be about 1050 fps. Are you saying that increasing the bullet weight and decreasing the mv will raise POI? Seems to go the other way with rimfires. It's certainly worth a try.

 

[matt7184]

Yes I am.

This "dwell time" relates to the time the bullet spends in the barrel. Even though this time is measured in milliseconds, it affects the elevation, The barrel will rise, due to recoil, before the bullet is completely out of the barrel. So the height of the front sight is established for a "standard" load, based on a bullet that takes "x" milliseconds to exit the barrel. If we increase the velocity of the load--either by reducing the bullet weight or increasing the powder charge--we reduce the amount of time the bullet is in the barrel and the load will shoot low.



Perhaps the best-- and worst-- example is the .38 Special. You can buy ammunition loaded with bullets from 110 to 200 grs. and at velocities between 730 and 1,000 fps. There is no way all of the loads are going to shoot to the same point of impact in a revolver with fixed sights. And there really isn't very much you can do about it except to stay with "standard" loads. If you want to shoot really light, fast bullets, you have to either accept that they're going to shoot low or modify your front sight.



Semi-autos are more forgiving than revolvers when it comes to point of impact shifts, and many of them have front sights that can be replaced. Here's the rule: If the shots are low, you need to lower the front sight; if they're high, you need to raise it.

http://www.findarticles.com/p/articles/mi_...ual/ai_61620977



This is a very good article and well worth the read time.



FWIW I use 115gr the most since it is also cheap and available cheap at Bass Pro or Wally World. 115gr in my Full hits "through the dot" at 7 yards, top of front blade at 15 yards, slightly above "through the dot" at 25 yards. 147 gr will bring the POI up. Not sure what load the M&P is sighted in for though, but im thinking between 124-147 gr since those are very common for defensive loadings.

 

[greener]

Bought some 147 gr ammo. Doesn't seem to make any significant difference. If I'm going to shoot this pistol with the tops of the rear and front sights even and the target "sitting" on top of the front sight, then it looks like my next range tool will be a flat file. One of us shoots consistently low.

 

[TXRedEye]

My 40 shot low and left when I got it, looks exactly like the same problem. I sent it back to S&W and they put a lower front sight on it. Works fine now except for the new problem with the striker. FYI

 

[greener]

Gave up on fixing the shooter since I seemed to get around POA with darned near everything else I shot, including a bunch I shot for the first time. Sent it to S&W and it was back in a week with a "replaced front sight note." Looks like a shorter sight. Assuming no hurricanes, tornado's, blizzards or honey do storms will find out if they fixed it in a couple of days.

 

[Smith Shooter]

Novak

Novak will be making an adjustable rear sight available for the M&P's in about two months. It will probably require a different froint sight too but I'm going to get them as soon as they are available. My M&P 9 seems to print low too.

 

[greener]

S&W did a quick turn around on the fix and it shoots well. However, when the adjustable sights come out, I will add it to the pistol.