My rifle is a Bushmaster lower with fixed tele stock with a Bushmaster post ban A3 16" M4 profile upper.

I was at the range today zeroing my iron sights when the rifle started to do somthing which I can't explain.

The first three  goups were almost dead center but still about an inch high so I lowerd the front sight post 1 click. After that all the groups were about 5 inches above the first 3.
They stayed up there no matter how low I set the front sight post. Even with the front sight as low as it goes the rifle still keept shooting 5 to 6 inches above the first three groups. I made sure I kept my sight picture the same and every thing. All the groups regardless of were they impacted the target were between 1-2.5 inches.

The distance was 50 yards and I was using XM193 Lot 43 with 02 and 03 on the headstamps.

The rear sight is a Bushmaster detachable cary handle.

Any ideas on what would cause this and or how to fix it would be much appreciated.

The front post moves towards the the group to zero, the rear sight will move away from group to center.  

If the rifle was shooting high, then you should have raised the front post.

You should have raised the front sight post 4 clicks.  Set your sights for mechanical zero and try it again.

Just remember "FORS" as it relates to sight movement/bullet impact

[b]F[/b]ront
[b]O[/b]pposite

[b]R[/b]ear
[b]S[/b]ame

[center]And now for a gratuitous graphic.[/center]
[img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=19412[/img]

Gun_Addict,
Your 16" flattop should have sight adjustments of .68MOA windage and 1.7MOA elevation. At 50 y[b]ar[/b]ds that's 0.34" W and 0.85" E.

If you changed the sight post one click the shot group should have only moved .85", not 4".

Either something is mechanically wrong (loose screws, etc.) or you're subconsciously holding into your sight adjustments, or both.

You're not using a bipod or a sling or something are you?

I figured out what was wrong.  The "up" arrow on my upper is pointing the wrong way.  When I turn it in the dirction of the up arrow it raises the sight insead of lowering it.  According to an e-mail I recived from bushmaster turning the post toward the up arrow should lower the front sight to rase the impact.

I know about the front opposite rear same rule but I was following the markings on the upper and it never clicked in my head that the sight should be moving up. [banghead]

Thanks for all the replies.

Uh, are you talking about the "UP" stamped into the flat on top of the FSB?[>:/]

Yep.

So the arrow is pointing towards the side of the weapon with the bolt release and safety lever?  Very interesting...

Thats right, it confused the hell out me.

I assume it's supposed point towards the side with the ejection port.

I had to go look at my Bushy to be sure, but my arrow is behind the front sight post and points to the side with the safety lever.  For some reason, I was thinking it was in front of the front sight post.  Anyway, if I turn it in the direction of the arrow it lowers the sight raising the point of impact.  

The threading on mine must have got screwed up some how than because when I turn mine toward the up arrow it rasies the post and lowers the point of impact.

Would that mean the threading on both the FSB and sight are backwards?

OK, all you guys ROTFL in the background STFU. He's new, he doesn't know any better. A thorough reading of Bradd_D's and Gun_Addict's post will show that G_A's "UP" arrow is not stamped the wrong direction. It is, as it should be, facing the left side of the rifle, the "safety lever" side.

I've been following along hoping the problem would get sorted, time to step in.

Gun_Addict,

You've just encountered one of the most confusing parts of the M series, the front sight post marking.

The problems are well known.

The "UP" is under the front sight post but is it the top or the bottom of the flange that needs to rotate in the direction of the arrow?

Does the "UP" mean movement of the front sight post or movement of point of impact (POI)?

It's about as counterintuitive as can be. Very confusing for n00bs and no doubt a primary reason behind the markings on the Army zero targets.

So, to clarify, turning the post [s]counterclockwise (CCW)[/s] clockwise (CW) (the direction of the "UP" arrow) lowers the post by screwing it in thereby raising the POI.

"Left loosey, righty tighty" applies.

Turning the post [s]clockwise (CW)[/s] counterclockwise (CCW) unscrews the post and raises it thereby lowering the POI.

Back to the original problem G_A. One click of front sight elevation will not move the POI 4", not with normal sights anyway.

[clarity]
[corrected CCW and CW]

I know this, my problem is when I turn it counter clock wise it unscrews and when I turn it clock wise it screws in.

P.S. I am not a noob I know how to adjust fucking sights and I damn well know that up means the point of impact for christs sake. And I DO KNOW WHAT DIRECTION CLOCK WISE IS SO DON'T BOTHER GOING THERE.

You controadic your self though

becuase left is counter clock wise and clock wise is right.

It is obvious now that you are suposed to go by the bottom of the front sight base. (this is assuming the muzzle is pointing up)

But this still means that clock wise raises the POI and counter clock wise lowers it.

I will assume that:

A. you made a mistake and ment it the other way around.

or B. you think that you tell clock wise and counter clock wise by facing the same direction as the clock. This is wrong.

Either way it dosn't really matter I was going by the top of the sight which is what one naturaly assumes instead of the bottom like it seems I should have.

Is this correct? Are you suposed to go by the way the bottom of the sight base turns? (again this is assuming the muzzle is pointed up)

Looking down on the top of the sight...if you turn the sight in the direction of the arrow (CW), it will lower the sight and raise the impact.  It's like driving in a screw.

Gun_Addict,
So down and take a deep breath, we all have our off color days, including Tweak.

To give you an idea of how mine went, I just got in an order from Wolff springs.  Started off by changing the recoil spring on my 92fs.  The spring came with an extra power firing pin spring, so I figured that I would just do a quick change on the firing pin spring (waiting for my wife to come home).  5 min in and all I needed to do is just re-install the safety. Well I managed to shoot the trigger bar plunger and spring across the shop. After looking for 10 min (steaming pissed), I gave up and will need to order a new one from Beretta USA tomorrow.
After finally cooling off over pulling a newbie mistake, I get back from taking my wife out to dinner and started on the 10 pack of Wolf springs for some 30 rounder that need to be re-sprung.  Get the pack open, and can't figure out why the springs are different than the last order I got.  Look at the pack and see that they are for 20 rounder. So it looks like I have to make two phone calls tomorrow and get parts/replacements.

To make my point, there are days when things are not clicking, and you just have to step back and re-group, even when your having a shit day. We all make mistakes, including myself, and shouldn't take the little misdirection’s in life so serious, nor point out others in a defensive way.
-----------------------------------------------
As for tweaks post of
"Turning the post clockwise (CW) unscrews the post and raises it thereby lowering the POI",
We all have our off days, with tweak just having a brain fart (reeking of CLP), and posted the wrong direction. I myself, have posted the wrong information many times over the years, and get corrected on a steady basses.  

The fun at this sight is the inside jokes all over the board, and catching the posting of wrong information (it gets really good when Tweak stays up all night, then tries to answer questions). What we have found is that all is needed to be done is to point out the mistake, and not make a big issue out of them.

I’m sure that Tweak will be along shortly, and have fun laughing at his mistake too.

I was turning it in the dirction of the arrow.

the arow points left so I turned the sight left.

How is right turning it in the dirction of the arrow if the arrwo points left?

Bingo,
Turning the post to the right (looking at the front sight post, with the barrel under the sight tower) will lower the post in the tower.  
This will raise the POI of the bullets looking threw the sights (the arrow direction on the tower), because you have lowered the front sight in the direction on where the barrel is sending the bullet.  The barrel is always going to shoot to the same point; it's where the sights are aiming that is changing.
The tower arrow is used for correcting directions on military targets, and not the direction that the screw will turn to move the post up or down.


For sighting corrections, it helps to draw two parallel lines (forget the front arrow on the tower).

The bottom line is the bullet path; the top line is the sight aiming point.  To get the two lines to intersect, you either have to lower the front of the top line (front sight) or raise the rear of the top line (rear sight).  For windage, just use two pencils pointing away from you, with the bottom one aiming at the point that the bullet is hitting the target, and the top pointing where the sights are aiming.  By adjusting the top pencil over to the bullet impact point, it gives you an idea of what direction the sight need to be moved to adjust the sights.

No offense but I know how sights work.

Perhaps I am confused on what the arrow means.

To me if the arrow points left that means rotate the sight to the left not the right is my brain just seeing it differntly or somthing?

P.S I am sorry about my previous post I am just fustrated and don't understand why  the arrow points left when you have to turn the sight to the right to move up POI.

The arrow is on the back of the tower (receiver side) and by screwing the post closest to the arrow (receiver side) in that direction (clockwise looking down), it will lower the post, hence raise the point of impact of the shot down range.

The post/arrow means to turn the closest side in that direction, not that the front (muzzle side) should be turned in that direction.  Think of the arrow as a circle that encompasses all the way around the front sight post, and means that clockwise movement will raise the POI down range (CW movement really just lowers the post, and make the sights point to where the bullet is striking).  

Thank you finaly some one explains it to me.  

So am I the only one was confused about this or what.

It seems to me thay should have made it less confusing.

[whacko]

Oh, I'm laughing alright Dano, not so much at my expense, but I am laughing, honest.

Dam, wrong twice in one day. Where DO I go to repent?

The CW and CCW got mixed in my halfas attempt at editing. So much for "clarity." [lol]

[rolleyes]

Just wanted to make certain that this part got saved in case of any future edits.

you are an ass

That may be but the true difference between you and I is that when I ask for help I accept it graciously.