Alright, so I was out shooting the m14 today with iron sights.


I was shooting groups of three and they would be PEERFECT windage wise, but were stacked on top of one another with about 3 inches between each.

What normally causes that?


One thing that I am sure of is that it was not caused by changes in barrel temp. I was firing around one round a minute.


I think it might have something to do with the bipod. I tend to get tighter groups using a sling, but they seem to be less consistant between groups if you know what I mean. I just can't sling up exactly the same every time.

Also check that the hand guard is not tightly fitted into the front band.

work on your basics before you troubleshoot a weapon.

velocity variations in ammo??????

I had the exact same thing with my AR - only it was literally a 6" string that was a perfect line up and down.  Don't know how I did it or what caused it and it never happened again.  It was just too perfect to explain it.  Normally you get a nice deviation all around the target area.  You'll probably never have it happen again....

1.  Are you using an M2 type bipod?  If so, you may have your culprit.  I've found that when using the M2 I can have wild groups, especially if I am putting pressure onto the bipod.  It's an MG bipod, not an accuracy bipod.  So, if you're using that type, stop.

2.  Sight picture.  Are you sure you're choosing the right sight picture every time?  For my part, centering the target horizontally is far easier than centering vertically.  That could just be my eyes, but at 100 yards I have to really concentrate on the sight picture I want, and then concentrate to be able to release a round when I see it.  Vertical strings have not proven uncommon in my experience.  But then, I'm no NM shooter, so YMMV.


In sum, it's my bet that the culprit is you (not in a bad way) just like almost every time something is messed up while I'm shooting, the culprit is me.

Consistant head position is crucial to acheiving a repeatable sight picture (the fact that you waited 1min between shots probably contributed to your stringing--shoot a 5 shot group at a normal pace without coming off the rifle each time and see what you get).

Anything that clamps onto the barrel or gas system is going to play havok with accuracy (bipod).

Work on your breathing.  vertical stringing is mostly caused by differences in the volume of air you have in your lungs when you fire.  Different volumes=different POI.  Remember to brath out 1/2 breath, hold for 3 to 5 seconds and squeeze the shot off.

This should stop your problem.

Quoted: Work on your breathing.  vertical stringing is mostly caused by differences in the volume of air you have in your lungs when you fire.  Different volumes=different POI.  Remember to brath out 1/2 breath, hold for 3 to 5 seconds and squeeze the shot off. This should stop your problem.

Breath control, along with velocity variances in the ammo are common causes of vertical stringing, BUT:

I have to argue your cure on this. 3-5 seconds and you start loosing vision. On top of that, how do you know you are holding EXACTLY the same ammount of air each time. The best method is to fire at the respiratory pause. That little natural hesitaion when you just finished taking in a breath and also at the end of the exhale. If your not thinking about breathing, you will take in an extremely constant volume, same when you exhale. It doesn't matter if you use exhale or inhale, just always do it at the same time. If you decide to go on the inhale, always go on the inhale, you will be way off on the exhale. Your NPOA should be set up for this point also. Get "Sight Alignment and Trigger Control" from Fulton. Unless you're shooting crappy surplus ammo, this is most likely your problem.

Quoted: Work on your breathing.  vertical stringing is mostly caused by differences in the volume of air you have in your lungs when you fire.  Different volumes=different POI.  Remember to brath out 1/2 breath, hold for 3 to 5 seconds and squeeze the shot off. This should stop your problem.

+1  I had this problem big time at our department's patrol rifle course.  Too many guys think if they don't shoot sub-moa it must be the gun or the ammo.  More than likely its something you're doing, and breathing is a big culprit.