iron sight alignment

[TSully]

First off, I am new to join although I have been visiting this site for some time now and it is far and above any other for quality content and ADULTS. I just recieved a new 14.5" midlength upper from BCM. I coupled that with a S&W M&P lower with a DD parts kit. I put on a Magpul flip up rear sight. When I took it out to zero my rear sight needed to be adjusted almost all the way to the left to get on target. I e-mailed BCM and they blew it off as if it was a non issue. My question is, should I be at all concerned about this? It seems it will be an issue for co-witness if nothing else. Is there some fix for this? Any imput would be greatly appreciated. By the way as you may have assumed I am relatively new to the AR platform. I have owned only Ohio legal hunting weapons until I purchased a DPMS sportical this past spring (laugh here!). However after research on this site I moved up. I think.

[sinlessorrow]

Have you tried letting someone with some time on the AR-15 shoot it?

You could have a canted front sight, but it could also be a number of other things as well. I always find it helpful when your having to really crank the rear to one side to have someone else shoot the rifle to eliminate user error.

Eta: where were the bullet impacting when you first had it setto a mechanical zero?

[IYAAYASwarrior]

x2 on letting another set of eyes give it a go

[TSully]

Yes, my brother in law shot it as well. He however, is less experienced with ar's than I am. We both have plenty of experience shooting other weapons i.e. shotguns, muzzle loaders, bolt action rifles. To get zero on the BCM the rear sight had to be set a couple clicks left of the second to the last hash mark. I didn't know if it could be the Magpul or the Fsb or if it mattered at all. As I said when I put a red dot on it I forsee it not cowitnessing

[sinlessorrow]

Yes, my brother in law shot it as well. He however, is less experienced with ar's than I am. We both have plenty of experience shooting other weapons i.e. shotguns, muzzle loaders, bolt action rifles. To get zero on the BCM the rear sight had to be set a couple clicks left of the second to the last hash mark. I didn't know if it could be the Magpul or the Fsb or if it mattered at all. As I said when I put a red dot on it I forsee it not cowitnessing

Ignore cowitnissing, both the irons and optic would have their own zero.

Any chance the magpul buis is canted when you installed it? Finding an experienced shooter is still ideal, BCM uses a bore laser to verify the FSB is straight but things do happen.

[TSully]

?I'll try to get out again this weekend but I am pretty confident in both my and my brother in laws abilities. I have been an avid hunter for decades. I was shooting 1to 2 inch groups at 100 yards I just thought my irons would be confusing to look at through an aim point being so far off center. Perhaps this is a non issue as I am easily hitting what I am aiming at. I just expected a little more from BCM from all I've read on this site.

[TSully]

O.k. I stuck a red dot from one of my shotguns on it and while I can access the irons through the R.D. I do not like the fact that they are off center. I guess I imagined I could sight in the irons then put the dot on the FSP and all would be in order. Not so with this set up.

[sinlessorrow]

?I'll try to get out again this weekend but I am pretty confident in both my and my brother in laws abilities. I have been an avid hunter for decades. I was shooting 1to 2 inch groups at 100 yards I just thought my irons would be confusing to look at through an aim point being so far off center. Perhaps this is a non issue as I am easily hitting what I am aiming at. I just expected a little more from BCM from all I've read on this site.

Shit happens. If you are getting 2MOA then your a good shot. More than likely the FSB is slightly canted, it wont make a difference with an optic. So you can either live with it(which wont damage the rifle) or contact BCM tomorrow and see what they say, make sure you tell them your fsb seems canted.

No matter who makes it, its still made by humans so things happen sometimes

What red dot on the shotgun did you use. Also while doing that will get you on paper usually the optic will have its own zero, BUIS are just that, back up iron sights.

[mdain]

Are you able to try a different rear sight? I'd be more inclined to believe the plastic Magpul sight is the culprit than the upper.

The only gun I have Magpul sights on is at work, or I'd take a look at mine.

[Slvr Surfr]

Another tip is to make sure you have a consistent cheek weld on the gun, making sure to have a repeatable contact point such as the tip of your nose touching the charging handle. That way the distance from your eyes to the rear sight doesn't change. This could effect zeroing.