I just purchased a M&P 15 OR, and installed a midwest industries rail and Magpul flip up BUIS. When zeroing the rifle, I was about 4" off at 25 yds. I had to move my rear sight about 1/8" to the left to be zeroed in. I just thought it was a lot of movement for zero. has anyone else had this problem?

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Are you sure that the sights are attached properly, not canted or anything and are flat on the rail?

I will take them off and reattach them. They are not listed as a same plane system by gunkings.com website. They are in the correct placement though. Front on gasblock rail, rear sight on the last slot.

BTW, the magpul shouldn't be used on the gas black due to heat.

What kind of "rail"? IF the front sight is on the rail and rear on the flattop, sounds like the rail is misaligned. Or are you are talking about a drop in type rail and are using the same plane gas block that comes on the rifle?

The magpul MBUS sights are not going to work on the gas block for the OR version. You will need a metal sight of some kind because of the heat. You also can't mount the sight on a drop in rail, because the rail is not solid enough. There will always be some movement in the rail and this will cause significant problems with accuracy. So to fix the issue you need either a metal front sight or a free float rail of some kind. Good luck.

Thanks for the advice guys. I am going to opt for a metal front sight.

So let me get this right. On my M&P 15 OR, I can use the Troy Industries or Yankee Hill folding sights, and they are same plane. I can also mount the front sight on my gas block. I am probably going to get better sights. The magpuls were thrown in with the rifle. Does anyone have a link to the sights, so I purchase the right pair.

http://www.primaryarms.com/images/12...701301404.jpeg

Troy Sights

(You do NOT want the one marked "gas block", it is too tall for your "same plane" gas block.

When I first got my M&P15OR I put on a pair of Magpul MBUS that I had purchased for a different project (I wasn't going to buy a M&P15 until this year, but last year the CDNN sale flyer, somehow caused a M&P15OR to show up at my local fun shop).
It was about 2" off (right also, as are you) at 25 yd to start. I adjusted it, and thought nothing of it.

The Magpul MBUS were fine for my first 1200 rounds, including too many mag dumps. I felt sorry for the front sight, as it was getting baked beyond it's design, but it never failed or lost zero. After cleaning it up, it looks and functions like new.

So unless your running full auto (with an M&P I'd think not), I wouldn't worry much about MBUS on the gas block, you just need to understand that if you bake it, Magpul will say we told you so. I'm assuming this is not a LE or fighting for you life situation, in which case get the best metal backup sights money can buy (I like YHM, but most prefer Troy which are very nice).

When I replaced the MBUS front with a YHM hooded folding front sight/gas block with rail, somehow it was dead on the first shot (at 25 yd). I call that lucky, and from a sample of one, nothing else.

It appeared dead on because the sight came already set up for "battlesight zero" and would appear dead on at 25 yards, however, simply hitting a target at 25 yards doesn't mean this particular weapon sighting system is accurate. The majority of mil spec sights for the weapon come that way for both front and rear.

There is a correct and intended zero method for the platform, despite its "sporting" use the platform is still a battlefield combat assualt weapon platform intended to be used with a certain sighting profile.

Factory or initial "Battlesight zero" the mil-spec sights come set for is not intended to be the final adjustment setting, its just intended to be able to put a weapon in the field without further zero and have a chance of hitting a man sized target within 100 meters, but not precisely or at longer ranges without further adjustments. Thats what the properly scaled military 25 Meter Zeroing Target for the M4 Carbine is for, and the reason for its use, to zero the weapon properly/accurately for out to 300 meters. Just hitting any old target with a X ring on it or a picture of some critter, in some sort of group, at 25 yards, does not indicate true (battlesight) zero for the weapon.

The weapon should really be sighted using the properly scaled military 25 Meter Zeroing Target for the M4 Carbine which will give the correct zero for the weapon. Just hitting any target at 25 meters is not an indication of accurate zero, it should be zeroed with a properly scaled target using the intended ammo for zero. The weapon platform was intended to be zero'd with either M193 (55gr) or M855 (62g) Ball ammunition (and not SAMMI spec .223 - regardless of barrel twist rate - the 1:9 barrel works fine with the 55 to 62 gr bullet), with properly scaled zero target, upon which the weapon 300 meter engagement range is based. You will notice the military 25 Meter Zeroing Target for the M4 Carbine says under the silouette on the zero target "300 Meters", there is a reason for that. Further "fine tuning" of adjustment can be done after that zero at actual target ranges of 100, 200, or 300 meters. It is not that the zero target physically is at 25 meters for zero, its the scaling of the target silouette and adjustment points of reference that make it the suitable target for zero'ing the platform.

It just so happens that an actual 200 meter POI shares a trajectory cross-over at 50 yards, with either M193 or M855 ball ammo. Most civilian ranges including some indoor ranges have this distance available. So you will be able to refine the battlesight zero at an actual 50 yard range for a 200 meter zero (although if you get the chance you should verifiy and adjust as necessary at the actual range of 200 meters). If you happen to have your own personal range space available, but not 200 or 300 meters of space, you should really be placing your targets for practice and fun at either 50 or 100 yards (these distances share cross over trajectories for M193 or M855 ball ammo) and not at 25 yards to start getting a more accurate picture of your skills.

The magpul sights don't come set up for real "battlesight zero" (and actually can not be adjusted to true "battlesight zero" although they can be adjusted very close), and the magpul sights are not mil-spec'd. Some people get away with using the magpul on the front gas block, for a while, but that should not be an indication of its continuing reliability.

Great info. Foxtrot. Have a link or source for that target?

Thanks, your expertise is appreciated and its refreshing to have an actual professional give the facts.

Edit: LOL, did search, found a great thread for targets............... http://www.m4carbine.net/showthread.php?t=43013

One place is > http://ohmr.ohio.gov/forms/ohmr2444-b.pdf

another is > http://nettopdf.info/download.html?d...- NCOSchoolcom

you can probably find them all over the internet via a google search > http://www.google.com/search?sourcei...73f91f3774c5c7

Or you can buy them also pretty cheap at various places such as > Law Enforcement Targets, Inc.: M4 CARBINE ZEROING TARGET. (use the M4 Carbine zeroing target side) - $0.21 per target - you only need a couple of them, heck, only one really as once your zero'd unless you do something to the weapon that causes zero to change, or remove the sights or put them back on you really don't need to zero again. Most people though simply download and print the target. You might even find them in various gun stores in your area.

A little note on the downloaded targets floating around on the internet, if you find it somewhere to download its important to make sure that when its printed out that its to proper scale on an 8.5 x 11 sheet. Some people for some reason rescale the target when making it available for download. We play it safe and just order a few then photocopy, or we borrow some from the local national guard unit. I'll bet that some if not most of you know someone in the military or national guard, or even with local law enforcement, that can get you a few of them also. Heck, a friendly and courteous phone call to a local national guard unit might get you a few of them.

You don't need a specal target to sight in any gun. Having a "properly scaled military 25 Meter Zeroing Target " may help if you have trouble converting inches to MOA, or need tips on which way to turn the adjustments; but it is not needed. Just remember at 25 yd 1" is 4 MOA not 1 (as it is at 100 yds). Know how to convert clicks (or turns or whatever) on your sight to MOA and it's all simple math.
The only really needed info from that target is the elevation adjustment. Right left is the same, no matter the distance (off course it scales with distance). If you are dead on at 100 yards right left, you will be 4x dead on at 25 yds. Even elevation can be made very close. Your line of sight is about 2.5" above the line of fire (optics/sights higher than barrel center). So if you want to be sighted for 50 yards, you need to be about 1.25" low at 25yds (assuming your not adjusting elevation on rear sight, or don't have it). A 5.56 bullet path is totaly flat at these distances.

I never suggested final sighting any rifle at 25 yards (well maybe the boys .22LRs). Some of us might have a 25 yd range very close, and need to drive 5 mile to get to a 100 yd range. So often the first shots are at 25 yard. Right/left evaluation are valid there. If you understand trajectory and math, you can also get really close on up down.

Wow, my magpul MBUS were off a whole 2" at 25 yards They must be junk I got them at a gun show for $80 a pair, and at that price point, I think they are awsome! Maybe someone played with the windage adjustment before I grabed them? Probably not but who knows.

Foxtrot -
"It appeared dead on because the sight came already set up for "battlesight zero" - if you follow what I said, it is a YMH front sight/gas block. It is unpinned block so to get my fist gas block swap (that is not pinned) to align so well on first try was very pleasing to me.

"The magpul sights don't come set up for real "battlesight zero" (and actually can not be adjusted to true "battlesight zero"
They don't have a Milspec elevation adjustment on the rear, is that what you are refering to? Thats because they are Back Up Sights. They have a large range of adjustment, mine zeroed fine at 50 yards which is how I like them, so that's how I set them. I can't understand how one could have any issue zeroing them in at any range.

Oh and no matter who you are or what you are shooting, it's always best to sight in you gun with the ammo you are going to use.

Well, there are various opinions and methods. The one I outlined is the correct method for the military type mil-spec iron sights.

Not to hijack this thread, but I think I made the same mistake. Have a 15OR and the Gen1 Magpul BUIS on front and rear. Front is on the gas block of course. Sounds like I need to go metal here. Should I ditch both front and rear or can I salvage the rear Magpul site? If I can keep it, what is recommended for a good match (metal) on the front? Not thinking about free-floating.

If you just want to replace the front with metal, then look for a same plane front sight. If you want a sight set then you also need a same plane system.