how do ultra dot's fail?

I bought a used pistol with an ultradot and during first firing I got the impression that during recoil the dot occasionally shifted.  I have two matchdot IIs and I don't get the same feeling, this one is an older 1" unit on a 45.   I would recover for the following shot and occasionally the dot would seem to be somewhere else, like at the top of the tube.   The zero was way off, so I had a hard time telling if my shots were grouping at first.   Later, they seemed to group OK, but I still had the feeling that the dot didn't show up where I expected it.

Could that be something loose inside the sight?   It is quite worn around the edges and the mount had a nick in it like it had hit something hard.

I didn't have a lot of caffeine today, honest!

I suppose any optic could take a hard enough hit to jar something lose or out of alignment. I have a hunting rifle with a scope on it and the scope took a hard enough hit to throw my elevation off by two feet a couple years back. Which is why I now go hunting with two rifles. An iron sighted back up rifle stays in the car in case something happens to my primary. That way all I have to do is go back and change guns and get back in the woods. 

Any chance Ultradot would take care of it under any kind of warranty?

Hang on tight and shoot off some sand bags.  See what happens.

Make sure the mount and rings are on secure.  Then, sight in the gun off sandbags at 25 yards.  If it fails to group, likely the scope is problem.

Your trouble sounds like a loose front lens.  The dot is projected against the inside of the lens and reflects back through the rear lens.  If either is loose, it can cause this trouble, but I think the front one is more critical.

Other possible trouble spots would be a loose diode or a dried out rubber pad that is used in the zeroing mechanism.  The rubber can dry out and harden.  This is less likely from your description, but it might cause your type of troubles.  However, I don't know how often that happens or if there was an environment issue that causes it, since there are a lot of old Ultradots still serving well.

If the lens is the trouble, you can probably fix that by tightening the lock ring from outside.  The other issues would need a pretty much total disassembly.

If your Ultradot has the square edged caps and no clicks in the adjustments, I don't believe it is covered under the warranty.

Thanks Ed, I had to remove the polarizing filter since there was some dried rubber/glue hanging down inside the filter.  I wonder if that indicates the inside rubber might be toast.

I will sandbag it with some decent ammo to see if it is a true problem or perhaps just me needing to recalibrate my eyes from my two 30mm tubed Ultradots down to the smaller 1" lens where perhaps the amount of movement seems greater than in the larger glass.

IIRC, there is an interior leaf spring that applies pressure against the tube that windage and elevation adjustments are made on.  It may be loose or broken.
Al

the leaf spring is what failed in my older 1" UD this year...

of course it was during a match...

the adjustments went to H*** and I was missing the target at 25 yds!!


only one I've had to fail..