Need Help sighting in a M&P 15

red1965

red1965

Joined
Apr 21, 2009
Messages
676
Hope some of you AR guys (and or gals) can help. I finally decided to zero my sights on my Smith M&P 15 (had been just using my AimPoint up until now) and I am not having any luck. Mine has the factory fixed front and flip up rear. Set it up where it was shooting about 2 to 3 inches low at 25 yds and when I moved out to 100, nada. Best I can tell its shooting low. I adjusted the front and tried again with no luck. Just to check that it wasnt me, folded the rear and shot with the AimPoint. Printed 5 for 5 in a decent little group. Anybody got any suggestions? Thanks
 
What rear sight are you using? What front sight do you have (Im assuming a F marked front sight) But Im not too familar with M&Ps.

2nd why are you setting it up to shoot 2" low at 25? I would follow these steps for the improved BSZ and report back... Courtesy of our friends at ARFcom.

http://www.ar15.com/content/page.html?id=599
 
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Ok, I will try to explain this better. This rifle has the standard fixed front AR sight. The rear is a flip up with no elevation adjustment, only windage. The link that was posted does not apply due to the fact that no elevation adjustment is possible with the rear. At 25 yards the gun should shoot 2 inches below point of aim due to the fact that the sights sit much higher than the bore, according to what I have read. The 2 inch low at 25 should pretty much be dead on at 100. I just want to use these as BUS as I use the AimPoint for most shooting, but one never knows when the batteries might fail. I have had no problems zeroing in the past with other AR rifles, but they all had A2 sights. Hope this helps to clarify my question.
 
I think what you're trying to accomplish is establishing what is called a "Maximum Point Blank Range/Battle Zero" (MPBR/BZ) with your BUIS (Back Up Iron Sights). There are several renditions of it and AR15.com has a bunch of them.

I'm not sure where your making the assumption if it is 2" low at 25 it will be dead on at 100 yards? Anyway if you are grounded in this assumption you might be disappointed.

Please keep in mind each gun and ammo combo is going to vary. Everything depends upon too many variables such as ambient air temp, elevation, humidity, barrel length, barrel twist, bullet weight, and velocity. So to say a given load will also do XYZ isn't always the case.

First, start with consistant ammo. I'd get 50 to 100 rounds from the same manufacturer (new not reloads) and preferable from the same lot. This will give you consistant DOPE.

Generally if you set a MPBR/BZ with a 55 grain projectile at around 3000 FPS from a 16" 1 in 9" barrel you should set the 25 yards zero at your front sight mechanical offset or roughly 1.5 to 2" low. Measure it to verify. Then your first intersection (where line of sight and line of flight meet or are dead on) should be in the 40 to 55 yard range not 100 yards. I know of one AR where it is at 32 yards.

At around 120 to 155 yards you'll achieved Maximum Ordinance (the highest it will reach) at about 3" to 7" high and then the second intersection (dead on) will be at 245 to 260 yards with your Maximum Point Blank Range at or around 280 to 300 yards (when it is back down to 3 to 7" low).

The whole idea behind MPBR is you can hold center on the thoracic cavity of your two or four legged predator and expect to get good hits without having to calculate a new firing solution or hold over or hold under.

Again, all of this is based upon too many numerous variables to list. Your mileage will vary for sure. The only thing you can do is take it out and find out where your first and second intersections are and your MPBR is.

I would suggest you establish a 25 yard Battle Zero of X amount of inches low. You can make the elevation adjustment (and always should anyway) at the Front Sight. Then start moving yourself back in 20 yard increments to see where you First and Second Intersection are and your Maximum Ordinance. Then type it up, print it and laminate it and tape it too your stock or put it to memory. Make sure you document the ammo, the FPS (Chrony is best), tempature, elevation, and humidity. REMEMBER if there is ever a 20/20/200 change this will all vary. In otherwords, if there is ever a 20 degrees temp change, and/or change of 20% humidity and/or change of 200' in elevation all of this changes! For a MPBR/BZ you will never need to make any elevation adjustments - only windage based upon wind conditions. That is the beauty of MPBR/BZ.

Finally, before you change too many things - ask a competent iron sight shooter to verify your POI.
 
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If the rear sight has no elevation adjustment, you're SOL if you want to establish a zero @ 100 yards.

You're going to have to hold over/under in some fashion.

However, it MAY be that it's the windage. Are you right or left @ 25? Small windage probs @ 25 magnify @100.
 
Ok, I might be off on the 100 yard theory. But... As I stated, the gun at 25 yds. is shooting 2 inches below point of aim. This is ok. At 100, I am not even on the target. I am using 55 grain Federal out of a 100 count box. Rifle is S&W M&P 15, 16 inch barrel with 1in 9 twist. Target is a standard IDPA with a paper plate stapled at center of mass. The rounds are not even hitting the target at 100 yards. POA is at the paper plate. I tried holdingat the bottom and top of the IDPA target just to check if rounds were going high or low. Nothing on target. I will try shooting at 25 and moving back in 10 yard increments to see what happens.
Quirt, the only thing I don't get is if the highest point of intersection should be between 120 and 155 yards, why am I not on paper? I don't know the exact size of the IDPA target but I am guessing at least 36 inches high by 24 inches wide. I should be hitting something.
Fubarski, rounds at 25yards were centered up. Shot 3 round groups to establish windage. First 3 were maybe 1/8 of an inch to the right. Shot 3 more to confirm and move the sight accordingly to center. Confirmed center with 2 more 3 round groups. All of these were impacting about 2 inches below point of aim.
 
Wish I was there to work with you personally...sorry bud....we can talk tonight by SKYPE or I can give you a call on my dime. Don't get discouraged - this will get figured out!

You could be off by windage or there could be a dozen other reasons why. 25 yards is very forgiving...100 isn't as much espcially with iron sights.

FYIW, I'm a Factory Certifed AR Armorer and I just repaired a rifle that the front sight base was slightly uncentered (the entire barrel was twisted because the barrel index pin was undersized) enough to be on at 25 and off at 100 yards. Crazy!

You're doing all the right things so far, so let's narrow this issue down some more:

Bore sight your M&P and here is how.... Take it to the range. Unload and separate all ammo away from the rifle. Field strip it and remove the bolt carrier group from the upper. Open the upper receiver but leave it pinned at the front or just remove the upper all together - whichever works best for what I'm about to share with you. Bag the upper or the entire rifle on a bench. Get is solid/stable.

Now get behind the upper and look through the breech (chamber) and through the bore to your IDPA target with a high Visibility larger center (orange or black paper plate - spray paint it if you have too). You're actually looking through the barrel and using it like a telescope. Center the barrel on the center of the paper plate on the bag.

Start with it at 25 yards and then do this again at 50 and then 100 yards.

Then raise up and look through your rear sight and front sight. The windage should be lined up. If there are any minor discreptancies at 100 yards this will show it - roughly. This is how you can bore sight an AR.

At 25 yards you're sights should be aiming at 1.5 to 2.5" low (measure your sight to see what is the mechanical offset). Then look through the bore - where is the barrel pointing at? At this distance you should be hitting exactly where the bore is pointed (low).

Then confirm your 25 Yard Zero. Change nothing. Move back to 50 yards. Verify your POA/POI. Make a note - where is it relative to your 25 yard zero. Now start moving back to 100! Document everything at each point. Now you should know closely where you're going to be shooting especially with windage cuz elevation is fickle because of the ballistics curve.

Make absolutely certain everything is tight on your gun - sights especially. If there is any movement or wiggle it will show up at 100 and beyond. Don't ask me how I know about sights wiggling lose - we won't go there!

Report tonight.
 
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Your front sight post should be adjustable for elevation (at least on every AR I have seen). Go back to 25 yards and LOWER it by screwing it down clockwise a couple of clicks at a time until you hit dead center at 25 yds. I would then move the target to 50 yds, fire a couple of groups to check point of impact. Adjust front sight again if required to hit dead center. Screw DOWN to raise point of impact, screw front sight out (UP) to lower point of impact. After you are satisfied at 50 yds then move to 100 yds for final tweaking.

All the theoretical stuff aside about where the sight adjustments are supposed to make the bullets hit, the KISS principle has always worked for me. My AR (Colt 6600) shoots pretty much flat between 25 and 100 yds with the issue sights. Make SURE your rear flip up sights are TIGHT before you even begin to shoot. Also, make sure you are shooting off a solid rest like sandbags. If you are freehanding then all bets are off.
 
Yup---you adj the front sight---it will be opposite of the std rear sight adj---meaning go down to come up.
 
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Guessing here, but if it has the standard AR front sight, you need to get the detachable handle rear sight.

If you just use a BUIS on the rear, and not a BUIS, standard AR style front, there is NO WAY you can elevate the rear enough, or lower the front enough.

BUIS rear, BUIS front =OK.

BUIS rear, standard front= No go.
 
If I am not mistake I own the exact same rifle, It has an adjustable rear sight...dunno at 50 yards mines DEAD accurate, haven't taken it to a range that has a further lane.
 
Most REAR BUIS are the SAME HEIGHT as the carry handle sight---unless you have something like the Troy Micro sight--which isn't meant for a normal AR flat top.

Most of the problems--come from an incorrect front flip up front sight--either mounted to a gas block rail or a "same plane" sight that is mounted on a hand guard rail. Make sure you have the right one for its application.

Since you have a normal FSB --you should be GTG----since a micro rear sight would be too low for your eye to see it with a normal cheek weld.

Another issue is do you have an "F" marked FSB? Bushmaster sells a different height front sight post to address this.

Also--are you positive you are shooting low? If you aren't getting on paper--you really don't know exactly where you are hitting----come back to 25 or even 10 yards to get on paper---keep in mind at exteme close range you will be shooting low due to the height of the sights in relation to the bore.

FBski's guesses are incorrect.
 
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If possible try to sight in at 35 not 25 m. As others have said, lower the front sight to )give slight (6 o'clock bullet hole seen above front sight, not covered by sight" This should give you about 1.5in high at 100m and about 2 in low at 200m. If you don't shoot iron sights regularly, the amount of "light" between front sight and target is critical and difficult to "remember". Be sure to shoot a 6 o'clock hold so you can really get a precise zero. You might print some inverted "T" targets with your computer to help get very precise windage. regards Les
 
Sorry, I may have mis read the original post. If you are trying to shoot point blank as "omaha" said the bore is lower than your sight line. Center line of my ACOG is 2.75 inches above bore. When shooting a "point blank" target (IPSC) I hold the top of the target or the 600m stadia line to get a center hit in the 6x6 head of the target. regards Les
 
What brand rear sight are you using, and are you switching apertures to go from 25 to 100? If you are using a rear sight without same plane apertures you will see a large shift at 100 yds when switching between the two.

2in low at 25 is correct due to the mechanical offset inherent with the AR.
 
Alright, let me answer some questions. For starters... I have previously owned AR's and I am fairly familar with their operation and sighting procedure. The ones I have owned in the past have either had a fixed or removable carry handle with the standard sights. The Smith is my first with a flip up non adjustable for elevation rear. I do know that elevation must be adjusted with the front on this model. The front sight is a F. The rear sight is marked with the S&W M&P logo. I know Smith uses Troy products but I am not sure that this is a Troy. Looks more like a Midwest Industries. It is not a micro sight. And no, I am not switching apertures. With the other AR weapons I have owned there was no need to switch unless I was getting past the 200 yd. range. I do have a Aimpoint red dot mounted which is set up to co-witness the irons.
I am not 100 percent sure I am shooting low, but from observing the dust cloud at impact it looks to be low. As for sight picture, I have been using a IDPA target with a standard paper plate stapled to the center of mass. My aiming point is the paper plate. I am not looking for a great group. This is a combat rifle and I expect combat type groups. If I can put a magazine full of rounds into the paper plate at 100 yds I will be done. For that matter, If I can put a mag full on the IDPA target, I will be done. I know its a matter of getting it adjusted due to the fact that with the Aimpoint I have shot pretty decent groups at 100 with this rifle.
I am still planning to take the gun back out and start at 25 yds. and work my way out to 100 and see what happens. Just havent had a chance to do it yet.
 
Sorry it has taken this long to reply (if anyone cares). I took the rifle back out and started all over. At 25 yards the rifle was shooting at approx. 2 in. below point of aim. Due to the crowd at the range, I was unable to move my target out in 10 yard increments, so my next group was fired at 50 yrds. The 50 yd. group was approx. 3 to 4 inches below point of aim. Moved one last time out to 100 yds. and group dropped to at least 1 foot below point of aim, but at least I was hitting on the target (Standard IDPA cardboard target). Checking to see if it was just my crappy shooting, I fired another 3 shot group at 100. Compared with my first 3 shot group, I ended up with a 7 to 8 inch group at 10 to 12 inches below point of aim. I have ordered a clamp on A2 sight that I am more familar with to try. I will give up the ability to just flip up the rear to be able to sight this gun in and be able to hit something at 100 and beyond with some degree of accuracy. Thanks for all the help and input.
 
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