What are signs of a scope slipping or not holding true?

[wahoowad]

I read a lot about scopes breaking or slipping - what are the signs this is happening while target shooting? Are there certain types of pattern/group behavior that suggest a scope issue over say a seal or hold issue? I would think the pattern might move but still be holding your previous group (jn general).

[Bentong]

Put a pencil mark on the scope tube and mount edge and to the tube and scope mount which attaches to the airgun. If you see the mark creeping away from where you mark it, you will know what's happening. Try here >>  http://www.pyramydair.com/site/articles/how-to-scope-air-rifle/

[djmyers]

For the scope slipping mine tilted as it slipped so was pretty easy to see what the problem was. When I had a scope actually break it was the magnification adjustment that went bad inside the scope and would loose focus with every shot.

When I blew the seals out of my gun it would not hold a group at all. Would get 1 or 2 in the same spot but most groups were 2-3 inches when they are usually 1/2 in. Took it home checked all the screws to make sure they were tight then ran through the chrony and was getting from 650-900! That's what was putting them all over the place. Replaced the seal and it's pin point again.

[airiscool]

When they break, some are obvious because they break lenses, or develop rattles from parts loose inside. Some AO scopes go out of focus after shooting. Some, like the Gamo scope that came on my Whisper, the retical turned slightly with each shot, so that now, the crosshairs have rotated counter-clockwise about 15 degrees.

Mostly, the scope fails to hold zero. It will group a few shots, then the next few shots will group somewhere else and you have to re- adjust windage and elevation to get it to group back where you want.  Moving in it's mountings, or the mounting moving on the gun, can cause a scope to exibit the same behaviour, so mark the mounts as Bentong mentioned to see if it could be, or is part of the problem, before giving up on a scope.  

Best way to tell if it's seal, or scope is change the scope and see it the gun still acts the same, or check the seal very carefully.

Paul.

[gmh45345]

What all have said plus on one of my scopes the crosshair seperated.
Gary

[RedFeather]

I've even heard of turrets popping off.

[djmyers]

I think my most obvious one was when I pulled the trigger and the scope and rings fell off the rifle! No doubt about it, it was not going to groups that way!