Scope tracking question/problem

[eric n]

Is it possible for a scope to have an INTERMITTENT problem tracking in the vertical plane only?
I have a sightron s111 that one day developed a 3 moa vertical shift (2 groups). It just so happened that I tried burning imperial out of the necks of this batch by annealing, instead of cleaning them out. I attributed the shift to neck tension, so after grabbing some proven rounds and shooting them, the shift was still there.
I did check all the fasteners for proper torque when I got home and all was well.
Pulled all the bullets, cleaned the necks and checked charges. Took the scope off to send back but thought i'd try it again with properly prepped brass. Tracked great.
Fast forward 700 rounds or so... Dialed in my come up today for 500yds, hit 1 moa low with very light 7 to 1 breeze. Dialed 1 moa up and bullets sail over target. Great, here we go again.
After dialing back down to original elevation, I started working back up one click at a time and shooting a round. Between 2 clicks, there is big vertical shift. (good ammo this time)

I know the scope is bad. I'm afraid it will "fix" itself and get a clean bill of health. I know nothing about the guts of a scope. Is it possible to have a problem intermittently like this?
One thing to add. I can't remember if the original issue I had was at 500 or 600 yds, if it matters.

 

[zolt]

I have a similar problem with a Leupold only mine is in the windage.

I have sent it back to Leupold for repairs 4 times and it still has the same problem.

I have tried it on several different good shooting rifles and the problem is still there.

I have a different scope on the original rifle and the scope sits in my safe.

 

[eric n]

That's a bummer. I hate how these inconsistent issues never happen for the mechanic
We'll see.
It sure is a good scope. If I equate it with how much money I put down barrels with powder and bullets, I feel I got my monies worth many times over.
Still can't wrap my mind around how it's happening

 

[boltfluter]

Had a Leupold that did the same thing in windage. Took them 3 tries but they finally got it fixed. What a pain to try and figure out.

Paul

www.boltfluting.com

 

[scott_at_vortex]

The main reason this can happen when scopes are sent in for repair is because the rings,ring torque(why a torque wrench is important), base(if it is two piece base) all can put tension on the scope tube which can affect the internals of the scope. So what happens is most guys take their scope out of the rings before they send it in and the scope performs great for the manufacturers technician. Certain rings are worse than others. However, if the base/action is causing the tension then there really is no way for the manufacturer to duplicate your set up(short of sending the whole rifle which I have asked some customers to do. I'm not sure how many other scope manufacturers have ffl's though and are able to do this).

All that being said, there really is one main part in a scope that could be affected by the mounting that could cause your problem. It is the erector tube gimble. It is basically a ball and socket that is on the rear end of the erector tube and sits right under the mag ring. Tension on the scope tube or distortion of the tube can change the dimension of the socket portion which will not let the ball move freely to the point that the erector spring is no longer strong enough to keep the erector tight against the turret, thus causing inconsistent adjustments. This is very similar to what caused old timers back in the day,and some still today, to religiously tap their scope after every turret adjustment.

 

[eric n]

Thank you for the reply Scott.

 

[fredhorace77]

I had a similar situation with a leupold, kept sending it in with a problem...came back with a problem. After 3 tries I took the turret cap off and proceeded to rap the daylights out of the turret with a rubber mallet until I could see parts rattling around inside the scope. Got a brand new one back in one and a half week, they finally found the problem . Honestly I don't know if they were truthfully looking into it in the first place.

 

[rifleman700]

The main reason this can happen when scopes are sent in for repair is because the rings,ring torque(why a torque wrench is important), base(if it is two piece base) all can put tension on the scope tube which can affect the internals of the scope. So what happens is most guys take their scope out of the rings before they send it in and the scope performs great for the manufacturers technician. Certain rings are worse than others. However, if the base/action is causing the tension then there really is no way for the manufacturer to duplicate your set up(short of sending the whole rifle which I have asked some customers to do. I'm not sure how many other scope manufacturers have ffl's though and are able to do this).

All that being said, there really is one main part in a scope that could be affected by the mounting that could cause your problem. It is the erector tube gimble. It is basically a ball and socket that is on the rear end of the erector tube and sits right under the mag ring. Tension on the scope tube or distortion of the tube can change the dimension of the socket portion which will not let the ball move freely to the point that the erector spring is no longer strong enough to keep the erector tight against the turret, thus causing inconsistent adjustments. This is very similar to what caused old timers back in the day,and some still today, to religiously tap their scope after every turret adjustment.

Finally some common sense when it comes to scopes. This is a common problem that few fail to see or admit. Thanks Scott!!