Iron Sights

hdwhit · #1 11-24-2016, 03:23 AM

I bought a S&W M&P-15 Sport II around the first of October. I took it to the family farm to sight it in using the sights supplied with the rifle.

It was a simple matter to get the right/left adjustment made, but I was unable to get the up/down adjustment made before inclement weather forced me to abandon the attempt.

This week, I tried again. At 50 yards, the rifle was consistently shooting low. The MBUS rear sight has no elevation adjustment, so I had to use the elevation adjustment on the front sight. Following the directions stamped into the front sight base, I was able to raise the point of impact to where the rifle was shooting consistently 1" to 1.5" low at 50 yards, but there was no adjustment left in the front sight. Has anyone else experienced this same kind of problem?

I removed the MBUS rear sight and replaced it with a carrying handle/rear sight assembly modeled on the M16A2. Within five three-round strings, I was able to adjust both the rear and front sight so that I was consistently able to cover my groups with a quarter at 50 and 100 yards and under 2 inches at 225 yards - not bad for a handicapped guy.

I also have an A2 style handle/sight assembly for the M&P-15 that I bought to teach my son how to shoot center-fire and will recommend he abandon the MBUS sight, too, if the front sight won't work with it as it failed to do on mine.

JaPes · #2 11-24-2016, 09:47 AM

Quote:

Originally Posted by hdwhit

I removed the MBUS rear sight and replaced it with a carrying handle/rear sight assembly modeled on the M16A2. Within five three-round strings, I was able to adjust both the rear and front sight so that I was consistently able to cover my groups with a quarter at 50 and 100 yards and under 2 inches at 225 yards

Congrats. You've discovered the singular advantage of an A2 rear sight (carry handle or chopped): the ability to adjust for both windage and elevation.

Rastoff · #3 11-24-2016, 10:21 PM

Hmmm, yes, I guess the rear A2 sight could be used to help zero the sights, but that's not what it's for. It is intended to be used to adjust for distance.

If there isn't enough room to zero elevation with the front sight, something's wrong. Even if you can compensate for it with the rear A2 sight, there's still something wrong.

Kadonny · #4 11-25-2016, 12:29 AM

Adjustments on the Sport 2 sights are very simple. To change point of impact up/down you adjust the front sight, to adjust the point of impact left/right you adjust the rear sight. Neither can do both.

Rastoff · #5 11-25-2016, 12:56 AM

Quote:

Originally Posted by Kadonny

Neither can do both.

Right, but he said he ran out of range on the front sight. It should have plenty of adjustment room at 50 yards.

Kadonny · #6 11-25-2016, 01:00 AM

Quote:

Originally Posted by Rastoff

Right, but he said he ran out of range on the front sight. It should have plenty of adjustment room at 50 yards.

Correct, but if you read his post in the other thread he claims the sights are wrong for the rifle. Most likely it's not the sights that are the problem.

Rastoff · #7 11-25-2016, 01:03 AM

Other thread? I'll go looking.

Yeah, if he has the wrong sights, that's the problem. Especially if he has a gas block that has a picatiny rail that isn't at the same height as the receiver.

Kadonny · #8 11-25-2016, 01:07 AM

I think his Sport was stock. So unless his rifle came with bad sights on it, then it's probably user error. Also, he was telling his son to take off the MBUS on his rifle too because they don't work, which is just not the case. The Sports MBUS work fine if you zero them properly.

Look at the "Any problems with the Sport" thread.

Rastoff · #9 11-25-2016, 04:14 PM

OK, found the other thread. Basically the same info as we saw here.

I'm sticking with my initial assessment. If the stock sights couldn't be zeroed, there's either something seriously wrong with the gun or he's not doing the process properly. Adjusting the elevation with a sight like this:

...is not how this sight is intended to be used.

Even if it works, with the front sight post all the way down, there is something wrong with his gun or technique. I'm leaning toward technique because there have been too many Sports sold for this not to have come up before.

cyphertext · #10 11-25-2016, 04:30 PM

Agree, he is most likely doing something wrong. If the Magpul sight is the wrong height as he suggests, it wouldn't be just a Sport problem... it would be the same on Colts or any other AR-15 with an F marked height front sight.

hdwhit · #11 11-25-2016, 10:04 PM

Quote:

Kadony wrote:
Also, he was telling his son to take off the MBUS on his rifle too because they don't work,...

Not at all. Please read the original post thoroughly. I said that IF he experienced the same problem with his, I would make a recommendation that he follow what I did.

As far as user error, I am certainly willing to concede that as a possibility, but when I was in the Army, I did qualify as Expert with an M-16A1 so I am familiar with the type. Also, I was on the rifle team when I was in college, so this is not the first time I have sighted in a rifle.

Rastoff · #12 11-25-2016, 10:09 PM

Look, if the rifle cannot be sighted at 50 yards with the sights it came with, there are only two possibilities; the rifle is broken or the user is doing it wrong.

Since you have a lot of experience with this rifle, I'm going to say you know what you're doing and it's not you. That only leaves the gun.

To test the sight, with your agreement, I will send you my address via PM and $6 to cover shipping. Send me your sight and I will test it to see if it's a problem. OK?

WVSig · #13 11-25-2016, 10:26 PM

Quote:

Originally Posted by hdwhit

Not at all. Please read the original post thoroughly. I said that IF he experienced the same problem with his, I would make a recommendation that he follow what I did.

As far as user error, I am certainly willing to concede that as a possibility, but when I was in the Army, I did qualify as Expert with an M-16A1 so I am familiar with the type. Also, I was on the rifle team when I was in college, so this is not the first time I have sighted in a rifle.

Have someone else who has experience shooting and zeroing the AR15 platform sight in the rifle. If they experience the same problem you did then call S&W and send the rifle in. There is something wrong with the rifle.

That said I doubt it is defective. This statement is telling.

Quote:

Originally Posted by hdwhit

So, my experience is that the Magpul MBUS sight is the wrong size and so doesn't work. When it was replaced, everything was quickly sighted in and the rifle worked fine.

Are you sure they are mounted properly? I would guess that there are hundreds of thousands of Magpul MBUS sights on rifles all over the world and they all should work with the standard A2 front post.

AR Owner · #14 11-25-2016, 11:43 PM

You can replace the front sight post with a shorter (non f marked) post i believe. Should be a .040 difference in height. I'm assuming you bottomed out the post trying to zero it.

Many places offer different sight posts in different heights and styles for a couple bucks.

AR Owner · #15 11-26-2016, 12:27 AM

Read this thread, could explain his dilemma. F marked front sight base - AR15.Com Archive

Rastoff · #16 11-26-2016, 12:41 AM

It could be the front sight post was the wrong height. That might account for his issue.

The thing I'm having trouble with is this is the first time I've heard of this. S&W has sold thousands of these and we've never heard of this before. Something is wrong. I hope it's just the post.

cyphertext · #17 11-26-2016, 12:55 AM

Quote:

Originally Posted by Rastoff

It could be the front sight post was the wrong height. That might account for his issue.

The thing I'm having trouble with is this is the first time I've heard of this. S&W has sold thousands of these and we've never heard of this before. Something is wrong. I hope it's just the post.

If it is the wrong post, we should start seeing more of these types of threads.

WVSig · #18 11-26-2016, 12:58 AM

Quote:

Originally Posted by AR Owner

Read this thread, could explain his dilemma. F marked front sight base - AR15.Com Archive

It could be a front post height issue but it would not be a one off issue. There would be hundreds if not thousands of rifles that would not zero. Since this is the first report of this kind I still am leaning towards user error or defective rifle.

AR Owner · #19 11-26-2016, 01:13 AM

1 wrong size front sight post may have slipped through the assembly, QC check. But regardless, it could be a simple solution for him to correct his problem.

WVSig · #20 11-26-2016, 01:17 AM

Quote:

Originally Posted by AR Owner

1 wrong size front sight post may have slipped through the assembly, QC check. But regardless, it could be a simple solution for him to correct his problem.

Maybe but seems unlikely. Based on the way parts are machines/manufactured these days if there is one the wrong size there are lots that are the wrong size.

Rastoff · #21 11-26-2016, 02:13 AM

I'll bet that S&W doesn't make anything but F front sights. Therefore, the taller post shouldn't even have been in the factory.

However, I have seen a 9mm case that was too long. So, as unlikely as it seems, it is possible. I wonder if we can get the OP to measure his post?

WVSig · #22 11-26-2016, 08:59 AM

Quote:

Originally Posted by Rastoff

I'll bet that S&W doesn't make anything but F front sights. Therefore, the taller post shouldn't even have been in the factory.

However, I have seen a 9mm case that was too long. So, as unlikely as it seems, it is possible. I wonder if we can get the OP to measure his post?

I agree with this. I am sure that they only use one sight. OP needs to measure the sight and take some pics or simply call S&W tell them the issue and I am willing to bet they send him a new one!

Kadonny · #23 11-27-2016, 12:27 AM

Quote:

Originally Posted by hdwhit

Not at all. Please read the original post thoroughly. I said that IF he experienced the same problem with his, I would make a recommendation that he follow what I did.

As far as user error, I am certainly willing to concede that as a possibility, but when I was in the Army, I did qualify as Expert with an M-16A1 so I am familiar with the type. Also, I was on the rifle team when I was in college, so this is not the first time I have sighted in a rifle.

You are claiming the sights are bad and wrong for the rifle.

Quote:

Originally Posted by hdwhit

So, my experience is that the Magpul MBUS sight is the wrong size and so doesn't work. When it was replaced, everything was quickly sighted in and the rifle worked fine.

That's just not the case. S&W has sold a TON of these rifles, if the sights were wrong there would be a whole bunch of people complaining about them.

Thank you for your service in the Army and I would certainly like to think you know what you are doing. But there is really only 2 possibilities here. One, your rifles sights are defective, or two it's user error. I'm sorry to say that, but those are the only options.

Steve912 · #24 11-27-2016, 01:53 AM

Quote:

Originally Posted by Kadonny

But there is really only 2 possibilities here. One, your rifles sights are defective, or two it's user error. I'm sorry to say that, but those are the only options.

3. Bent barrel.

ChattanoogaPhil · #25 11-27-2016, 09:06 AM

Don't overthink it... first things first.

Assuming the shooter is at 50yds not 50 feet and it's not operator error.

Disassembly and inspection takes about 30 seconds
Check if the detent is not freely moving far enough down.
Checks threads on the post/base are boogered/debris.

Here's a pic I took for those who may have never fooled with it.
It's been a long time since I broke open my 1983 Technical manual.

vonn · #26 11-27-2016, 09:35 AM

Interesting thread awaiting resolution. Posts that make you think about how things work together help us all become better riflemen. Simple everyday things that go wrong always cause me the most problems because they are things I do without thinking them through.

ChattanoogaPhil · #27 11-27-2016, 02:57 PM

Quote:

Originally Posted by vonn

Interesting thread awaiting resolution. Posts that make you think about how things work together help us all become better rifelmen. Simple everyday things that go wrong always cause me the most problems because they are things I do without thinking them through.

Right. It's the simple stuff that usually gets ya.